I'm running into multiple problems with Thunderbird (version 78.5.0, on Windows 10); here's the description: For several years now, I've had three email accounts (two Gmail, one Hotmail) attached to Thunderbird. One of the Gmail accounts is generally dormant, but I use the other Gmail address and the Hotmail address frequently. Two days ago, I clicked on the frequently-used Gmail account name (the bold name down the list, not the subfolder under Inbox), and then explored that account's various subfolders (junk, etc.). When I returned to the unified Inbox, all the emails from that Gmail account had disappeared. The emails were still visible if I clicked through to the individual account as described above. Today, I realized that none of the three email accounts were loading new messages. The "Get Messages" function did nothing. I tried various fixes I found online. Nothing worked. I then removed both Gmail accounts from Thunderbird and tried re-adding them, but the re-add procedure always failed. My name, email addresses, and passwords were all entered correctly, and I used the correct IMAP settings (I used Thunderbird's configuration wizard, and when I doublechecked using the "Configure manually" button, everything matched Google's recommendations). However, every time I clicked "Done," I received the yellow-box error message reading, "Unable to log in at server. Probably wrong configuration, username or password." Then, after each time I abandoned the re-adding attempt, the script at the bottom of Thunderbird's main window still read, "Mail for ''my.alias''@gmail.com@imap.gmail.com: Connected to imap.gmail.com..." In short, I'm stuck. Help, please.