Have you tried restarting your windows device? It is always the first step and so often overlooked. If you have a WiFi modem or other routing device you should restart all of them.

Mine hasn't received new messages since June 13, 2023 (very similar to the above thread) I've restarted the laptop many times since then. I've tried it on completely different wifi's when I travel. Those things don't seem to have anything to do with this problem. Is there something else? Maybe more specific to Thunderbird and the settings?

I keep getting "invalid password" when it checks one of my accounts (password is valid and works for other email systems). It then crashes and I have to exit the program. I have changed to a different system (Postbox) but would prefer Thunderbird if at all possible.