Tbird frequently will not download emails from the server that are there. My phone has no problem

About a week or so ago my Win11 laptop stopped downloading my emails reliably. When I open Thunderbird it goes to the server and then to the server inbox and then closes down. This happens most of the time. Occasionally it randomly will download all of the emails accumulated that it had not downloaded before although I haven't done anything differently that I'm aware of. I use Network Solutions to host the email server. I called Network Solutions and they could see nothing wrong. The only thing I see that was not happening before is that I am getting an inordinate number of threat Mcafee popups that I can't seem to stop. I don't know if this has anything to do with it. This has been incredibly frustrating because I don't know what to do. Any help is more than appreciated! It says Thunderbird is up to date and I think the version is 153.6.0esr(64Bit)