I had a teamname.1password.com, my.1password.eu and teamname.1password.eu. Deleted the .com account per account migration (com/eu) instructions and after that, 1passwordx was unable to unlock again until browser had been restarted (or ChromeOS in the other case).
I think it said something like "Unable to unlock, check your internet connection and retry" (sorry for not having exact string).
Same happened both on Firefox 60ESR on Linux and ChromeOS75, 1passwordX 1.15.6 on both.
Android client only got upset and gave me a confusing debug log of the background sync stuff, but didn't fail more than that.
Possible(?) way to reproduce:
Create a few accounts (2?)
Add them to 1pX
Delete one of them (perhaps the main/top one?) through web page while still being signed in (but locked?) in the browser.
Yeah, I should probably have signed out first - but still..
1Password Version: Not Provided
Extension Version: 1.15.6
OS Version: Linux&ChromeOS
Sync Type: Not Provided