Reinstallation of Thunderbird on new computer has Network Protocol Error/Authentication Failure
Have successfully installed and used Thunderbird on new desktop computers multiple times, but can't do final step(s) on this one. Mail provider is Gmail, ISP is (Emporia KS) ValuNet Fiber, using Windows 10 Pro, Malwarebytes anti-virus and firewall. Download and installation of latest version of Thunderbird works fine, including automatic recognition of account. As shown by attached images, normal home page is present, except dot beside "Inbox" at extreme upper left keeps on bouncing, and (attached image of) Google sign-in window immediately appears. Use of Google password then results in error messages of "Authentication failure while connecting to server" or "Network Protocol Error". As shown by attached image, SMTP settings are correct. All other Internet (via both WiFi and Ethernet) work fine, as does installation and use of (non-preferred) Outlook mail provider. Troubleshooting efforts of multiple attempts of uninstall and new downloads, obtaining new Google password, manual setting of server settings (including trying POP), and shutdown of Malwarebytes have proven ineffective. ValuNet Fiber ISP has checked incoming service and pronounces it in good order. What am I missing? Thanks.