I am using the most recent version of Thunderbird (78.13.0 (64-bit)), and during the past few days there has been a problem synchronizing with IMAP folders. The folders I have set up on the server do not appear (I can still access them through MS Outlook) and, more significantly, common folders ("Drafts", "Sent") will sometimes appear, most times not. When I go into my account and change the "Subscribe" options, shut down Thunderbird and restart, the folders will momentarily appear and then once again disappear. A similar thing happens when I "Subscribe" to the folders and then hit "Refresh": all of the check marks I have put in disappear. I have not changed any of my server settings, and those settings are the ones specified by my IT crew at the university. On some occasions, sent mail and drafts go into the appropriate folders (which then appear); on other occasions, Thunderbird just keeps spinning with no results (even though Outlook shows the messages have been sent or saved in drafts). Any suggestions for how to fix this glitch?