Problems began to pile up for Creative Cloud beginning around 3:00 p.m. Eastern Standard Time on Wednesday, when some users found themselves unable to download applications. That was followed by an issue with modifying team accounts, failures affecting the ability to purchase new Creative Cloud subscriptions or create new Adobe IDs, and finally the sign-in problem.
Adobe has been largely silent on the subject since Wednesday evening, save for a handful of apologetic tweets and a promise to "restore as soon as possible." The root cause appears to be a failure of the Adobe ID system, which is to Adobe's products what the Apple ID is to Apple devices and services.
Because Creative Cloud applications require users to be online to verify their subscription, subscribers who already have the software installed may be able to work around the authentication problems by taking their computer offline before opening the applications.
Adobe stopped offering standalone versions of their popular Creative Suite last year, forcing those who wished to upgrade to the newest edition to purchase it on the Creative Cloud subscription model. Many users criticized that decision, often citing potential scenarios much like this one.