I'm trying with utter lack of success to configure a Thunderbird install to link to a Gmail account via IMAP. System Basics: Windows 10 Home, 64bit, fully patched. Antivirus by MalwareBytes 4.30 Premium, fully updated. No fancy firewall, just a regular router. This account had been installed and working fine until a family member "helpfully" changed the Gmail password, but reauthentication fails. I enter the account details, including password, into the Thunderbird Accounts settings for the account; it pings Google and correctly retrieves all the IMAP settings, and when I click "Done" Thunderbird opens a browser window to Google's two-step authentication with the email address prepopulated. However, when I click the blue "Next" button on that authentication page, rather than advancing to a password screen, the browser simply deletes the email address from the text box and stays on the same screen (see attached image for what I'm talking about). Things I've tried: * Uninstall, reboot, reinstall Thunderbird. * Turn off MalwareBytes protection. * Uninstall, delete every registry key related to Thunderbird, reboot, reinstall Thunderbird. * Clear cache on every browser on the system * Change Windows default browser settings to either Chrome (see below) or IE/Edge * Install new browser (Chrome wasn't yet on this PC), then change Thunderbird's file handler for https to Chrome (this is MUCH harder than it used to be as T-Bird v. 78.anything doesn't have the old "Preferences" menus) Incidentally, changing browsers doesn't seem to make a difference in that pop-up browser window, so I suspect Thunderbird is using its own internal browser and not the system browser. I have, and can send, the support info extract from T-bird to a support technician but am unsure of uploading it here. Nevertheless, I welcome suggestions ... this is driving me nuts!