Rated 5 out of 5 stars

This has been my forever great app in Firefox.
Now since last week ~25-feb one of my account fails to login.
Credentials are fine.
I removed and added account. This even with first removing, then restarting FF 27.0.1, adding account.

It is my Google Apps account instead of my few other regular gmail accounts. I believe that is the problem. Because I check with other Google Apps accounts (family members) and the same issue.

So it looks Google likely changed something on the authentication.

Then I read down and I downloaded: Thnx Tommy & Erik for supporting this add-on :-)
https://github.com/twang817/firefox-gmail-manager-ng/raw/fork/dist/gmail_manager_ng-0.6.5.2.2.xpi

This solves the issue. This version or a next version with this fix should be pushed to the official Firefox apps repository.