Posted 01 March 2017 - 11:24 AM
Were I you I would just delete the accounts in Thunderbird and re-create them. With IMAP access all your messages are stored on the server so you just get them all back when the account is created anew again.
I really have no idea why this would occur suddenly. I've got Gmail accounts setup in MS-Outlook 2010, Thunderbird, WLM 2012, & Opera Mail and they've been and continue to be working fine in all of them. All I can imagine is that "something burped" in Thunderbird itself that's causing the issue. Removing the account and re-creating it should at least tell you whether the problem persists.
Brian AKA Bri the Tech Guy (website in my user profile) - Windows 10 Home, 64-Bit, Version 1809, Build 17763
Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.
~ Mark Twain