I have been using Thunderbird for years now, but it recently started downloading only 15-20 messages at a time, and I have to hit "get messages" again to get more. This is causing the inbox to get farther and farther behind, as it will not download more until the "Get Messages" button is clicked. I just figured this out, and had to hit the button many times to catch up to the latest messages. This has caused me to miss a couple important emails, because it has always downloaded ALL new messages when starting. Any ideas on how to fix this? I have looked at all the settings in both Thunderbird and Gmail to find anything that would cause this, but see nothing wrong.

Thunderbird 78.3.2 POP account on Gmail.