Unable to connect to Wi-Fi network "The Wi-Fi network " " could not be joined."

Posted:
in Genius Bar
Evening all,

My first time on these forums, so hoping someone could offer some assistance with this issue.

I have a 2015 iMac with 5K Retina Display that is experiencing a curious fault. It is currently unable to connect to my home Wi-Fi network and displays the following message whenever I try and connect:

"The Wi-Fi network " " could not be joined.
Try moving closer to the wireless router. Alternatively run Wireless Diagnostics to troubleshoot."

The iMac is in a location with a strong Wi-Fi signal and all other devices within the same location can connect to this SSID (including the MacBook Pro on the same desk as the iMac on which I am typing this). I have used Wi-Fi explorer to troubleshoot, and can see no issues with the strength of the network, interference from other channels etc.

I have tried deleting the SSID from KeyChain, and then re-connecting from scratch to no avail. I took the iMac into the Genius Bar but when tested, it connected immediately to the in-store Wi-Fi without any issue. I also have a separate Windows 10 Bootcamp partition which can connect to the same network without any issue, which would seem to rule out hardware. The only thing that they could suggest following my own triage, was to re-install OSX which I did, and which did appear to fix the issue. Upon a subsequent boot-up of the system however, the fault has re-occurred again.

I am an experienced IT Support Engineer with a strong Windows background (still making the full adjustment to Mac), and am at a complete loss to explain this behaviour. Clearly, this is not hardware else the Windows partition would also have issues and I could not connect to other networks. Likewise, this is clearly not 100% software, as the iMac can connect to all other networks tested. Finally, this is clearly not 100% a router issue, as every other device in the house can connect without issue including other MacBook's, iPhone's etc.

suspect that some corruption has taken place deep within a config file that is then being cached for this SSID specifically, however I have not been able to evidence this, and likewise would have expected the re-install of OSX to resolve this type of fault. 

Can anyone offer any other suggestions for where to go with troubleshooting this issue?

Regards,

gdthreepwood

Comments

  • Reply 1 of 7
    MarvinMarvin Posts: 14,200moderator
    If you open system prefs > network > wifi, set the network to the one you want in the drop down. Then click advanced. Check what IPs are being assigned in TCP/IP. IPv4 should be set to get an IP via DHCP.

    You can also try creating a new user on the system and seeing if that user can connect ok. If the new user can connect, there may be a setting somewhere in your home folder affecting connection.

    You can also check the router's wifi setup. Routers can be set to different standards (802.11b/g/n/ac) and different encryption methods. You can try disabling encryption to see if it will connect. There are some other suggestions on the following site with locations of internet settings files:

    http://www.chriswrites.com/how-to-fix-wifi-connection-problems-in-mac-os-x-lion/
    MegeByte
  • Reply 2 of 7
    Marvin said:
    If you open system prefs > network > wifi, set the network to the one you want in the drop down. Then click advanced. Check what IPs are being assigned in TCP/IP. IPv4 should be set to get an IP via DHCP.

    You can also try creating a new user on the system and seeing if that user can connect ok. If the new user can connect, there may be a setting somewhere in your home folder affecting connection.

    You can also check the router's wifi setup. Routers can be set to different standards (802.11b/g/n/ac) and different encryption methods. You can try disabling encryption to see if it will connect. There are some other suggestions on the following site with locations of internet settings files:

    http://www.chriswrites.com/how-to-fix-wifi-connection-problems-in-mac-os-x-lion/
    Hi Marvin - I've just been through all the troubleshooting steps you have suggested and unfortunately nothing worked. 

    I am unable to see any IP's assigned to the interface as I cannot connect to the Wi-Fi. When I could connect following the re-install of OSX, this was set correctly to receive it's address via DHCP.

    I have tried creating a new user account but still receive the same error.

    I have also disabled encryption on router, still cannot connect.

    Finally, I've worked through all steps suggested in the link provided, but I am still at square one.

    Do you have any further guidance?

    Regards,

    gdthreepwood



  • Reply 3 of 7

    OK - this is interesting. I've managed to force a connection using the following terminal command:

    networksetup -setairportnetwork en0
    WIFI_SSID_I_WANT_TO_JOIN WIFI_PASSWORD

    However, although the network is connected, I am seeing significant packet loss when running a continual ping, and there is a huge amount of latency on the responses that are received. Attempting to access even simple websites results in a timeout. I have managed to get to this position once before, however upon a reboot of the system, the connection was lost and I was right back to square one. 

    
Does this provide any further evidence to suggest what is at fault here?

  • Reply 4 of 7
    MarvinMarvin Posts: 14,200moderator
    Check your console log (/Applications/Utilities/Console) when you connect to the network, that will give you some info about what it's doing.

    One thing you might be able to try is connecting the Macbook Pro to the router using an ethernet cable and then enabling internet sharing in system prefs > sharing. You'd share the network on the Macbook Pro from ethernet to wifi. This would turn the MBP into a router. You can then check if the iMac will connect to that wifi network. If it doesn't, there might be something wrong with the iMac wifi hardware.

    If the iMac's wifi is faulty, there's hardware to get round it like the following:

    https://www.amazon.com/TP-LINK-TL-WR702N-Wireless-Repeater-150Mbps/dp/B007PTCFFW

    You could put that into repeater or bridge mode. You'd connect it wirelessly to the router and you can connect it to the iMac over ethernet or via wifi if it works.

    You can also try booting the iMac up from the system that's on the MBP by putting the MBP into target disk mode and connecting it over Thunderbolt:

    http://www.howtogeek.com/214322/how-to-boot-your-mac-in-target-disk-mode-for-easy-file-transfers/

    You'd set the MBP to target mode, connect it over Thunderbolt, hold alt when booting the iMac and choose the drive to boot from it. That will run the iMac with the MBP's OS and settings to see if that system will let the iMac connect. You can also clone the MBP's system to an external drive using an app like Carbon Copy Cloner and boot from that.

    There's another site here with more suggestions:

    http://www.igeeksblog.com/how-to-fix-wi-fi-issues-in-mac-os-x-el-capitan/

    Booting into safe mode by holding shift at boot clears out some caches so that's something to try too. You can also run a hardware test to see if that shows anything wrong:

    https://support.apple.com/en-us/HT202731
    MegeByte
  • Reply 5 of 7
    OK, following the steps suggested in http://www.igeeksblog.com/how-to-fix-wi-fi-issues-in-mac-os-x-el-capitan/, has got me connected to the Wi-Fi (following the creation of a new location, DNS entries and a manually configured MTU). Although this has got me connected, I am still suffering with terrible latency and packet loss and attempting to load any website results in a download speed akin to a 28.8Kb/s modem.

    Does this help somewhat?
    edited June 2016 MegeByte
  • Reply 6 of 7
    MarvinMarvin Posts: 14,200moderator
    OK, following the steps suggested in http://www.igeeksblog.com/how-to-fix-wi-fi-issues-in-mac-os-x-el-capitan/, has got me connected to the Wi-Fi (following the creation of a new location, DNS entries and a manually configured MTU). Although this has got me connected, I am still suffering with terrible latency and packet loss and attempting to load any website results in a download speed akin to a 28.8Kb/s modem.

    Does this help somewhat?
    There seems to be quite a few people with similar wifi problems in El Capitan, there's 12 pages of comments:

    https://discussions.apple.com/thread/7260515?t=0

    If your working computers are on a different system, it might be an OS issue. Some people there reverted to Yosemite, some reset their PRAM ( https://support.apple.com/en-us/HT204063 ).

    There's a hidden diagnostic panel you can look at. If you hold the alt-key when clicking the wifi menu, there's an option to open wireless diagnostics. Running through that will generate log files and find issues with the connection. It generates a compressed folder of log files on your desktop. You can also use the window menu on opening diagnostics to run scans and look at some of the wifi logs individually:

    https://support.apple.com/en-us/HT202663

    There's an SNI graph under window > performance to show if anything is interfering with your connection. Make sure that you don't have anything wireless near your iMac that could be affecting the signal like a cordless phone or baby monitor or anything like that.
  • Reply 7 of 7
    I'm facing the same issue, But I got it fixed by changing Wi-Fi channel in my router. I figured out my neighbor and I was on the same channel and his network signals were interfering with my Wi-Fi signals. So I changed my wireless channel from 1 to 11 by logging into the router and changing wireless settings.
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