It doesn’t matter how long ago you used TestFlight because I haven’t used it for almost a year now, nor do I still have it installed.I have an account associated with testflight, but I haven't used it for months. I ask, how can it be a testflight problem, if last week I updated it without problems, and from yesterday to today I already stopped doing it
However, it seems that any Apple ID’s that ever used it are now glitched due to a programming error made by someone at Apple.