- I get to the stage Mozilla Thunderbird Email wants to access your google account.
- When I click Allow, instead of finishing the setup, it brings another popup window: Authentication required - Mozilla Thunderbird.
- No matter what I enter there (full gmail address, just the gmail name etc), it's not accepted, and the same window pops up again and again.

I've been using Thunderbird for years with multiple google accounts on both Windows and Linux machines, no issues. On my main Windows computer one of the accounts started asking for authorization on a regular basis 2-3 months ago. I deleted the account, hoping to fix the issue, but when trying to add it back, I am stuck with this persistent issue: - I get to the stage Mozilla Thunderbird Email wants to access your google account. - When I click Allow, instead of finishing the setup, it brings another popup window: Authentication required - Mozilla Thunderbird. - No matter what I enter there (full gmail address, just the gmail name etc), it's not accepted, and the same window pops up again and again. I tried to reinstall Thunderbird a couple of times, and also deleted all files inside C:\Users\xxx\AppData\Local\Thunderbird and C:\Users\xxx\AppData\Roaming\Thunderbird . No change. The issue affects only this particular computer, only this particular gmail account. All other gmail accounts work fine on this computer, and on my other computers (Linux and Widnows ones) all gmail accounts work fine, including the one which I am struggling with on the first computer. There seems to be some caching going one which cannot be defeated by uninstalling Thunderbird and deleting the two C:\Users\xxx\AppData\*\Thunderbird folders. Where else can it be stored? Could it be Windows registry file? Thank you in advance.