About to get locked out of my Pocket account, any suggestions?

For weeks, Mozilla has been warning that Pocket accounts need to change to use Firefox logins. I have been trying to do so, including attempting from four different browsers on three devices, three different internet connections. I cleared the cache, data and cookies on the browsers, cleared the data on the Pocket app (losing my backed up library), and tried removing Pocket from the list of services that can access my firefox account in an attempt to re-add it.

Despite these efforts, I still just get stuck in a loop where I attempt to use my firefox login and never am able to authenticate, getting thrown back to the main login screen over and over.

Pocket support has been no help, suggesting only the solutions I've already tried, so it looks like I'm about to lose my account with thousands of articles in it that I've been a paying subscriber to for years. I was able to port my library to Omnivore which I will start using if I lose access to Pocket. Has anyone experienced anything like this, and how did you break the loop?