Not responding may be caused by an Anti-Virus which is scanning files etc. Exit Thundrbird. '''Firewall:''' Access Firewall - it might be the defaulton computer or controlled by an Anti-Virus prgram. Set up Thunderbird program as 'allowed' so nothing gets blocked. * Confirm Thunderbird is set up as allowed program. '''Anti-Virus:''' Access AV and set up to exclude scanning of your Thunderbird profile folder. If you installed Thunderbird from the official website: https://www.thunderbird.net/en-US/thunderbird/all/ Then profile will be here - this is the 'Thunderbird' folder you need to exclude. C:/Users/username/Appdata/Roaming/'''Thunderbird''' * Confirm you have set up to exclude scanning of profile. '''VPN:''' Check computer for a VPN. Some Anti-Virus products now offer a VPN and I have come across some peopl who did not realise one had been enabled. Switch off VPN (or create split tunnelling and set it up for Thunderbird to use). Gmail does not like VPN as it atempts to hide your IP address, so gmail decides you might be hacker so it auto blocks access. * Confirm VPN is switched off * What OS are you using ? * What version of Thunderbird are you using? * Where did you get the installation download from - Sna, Flatpak. Windows App Store or the official website? * What Anti-Virus are you using ?