I have to switch folders to see the inbox

On my Outlook 2021 for Windows 11, I have to switch folders to see what new e-mail just came in, if any. For example, I launch Outlook, it connects and does the IMAP sync. The Inbox shows no new e-mail. So, to see if I really do have new, unread email, I have to go to any other folder, wait a second or two for the IMAP sync to finish, then go back to the Inbox. If there are new messages, only after doing that will I see them.

Background info:

New computer, bought May 2025 because old box couldn't be updated to Windows 11. I don't remember this problem on the old computer. I think it started after I loaded everything on the new computer.

A month or so ago, I had an unrelated problem that led me to totally wipe Windows and start over from the Dell image. Reloaded Office 2021 (I believe it is the standalone version, not M365) and this problem continued. 

There are two e-mail accounts in Outlook, but only one is affected. Both use IMAP. Yahoo.com works just fine. It is Spectrum.net that is having this problem.

Anyone have any ideas where to start? And yes, I did verify the Spectrum IMAP settings; I can get and send email just fine. The problem is, new e-mail doesn't display unless I do the dance decribed above.