Thunderbird keeps asking for my passwords and no longer download emails unless I close and reopen the program (locked duplicate)

As of a few days ago, popup boxes have been appearing where Thunderbird is asking for passwords for my email addresses (I access emails from four different addresses with Thunderbird). Sometimes I will get the same popup box for a specific email address appearing several times over a few minutes. I reinstalled Thunderbird hoping that would help, but, while the popups are less frequent, they are still happening. Also, while I have Thunderbird set up to check for new emails every 10 minutes and to download them automatically, it is only downloading emails when I shut down the program and restart it. "Get New Message For:" does not work. I know that new emails are not being automatically downloaded as I see that there are new ones at the website of my ISP. Most of the solutions I have seen are not current, and reference settings I cannot find in my version. I have tried deleting and reentering the passwords by clicking on Saved Passwords in settings, but that did not help. Any suggestions?