Found an interesting bug with IMAP.
IMAP shows mail from current to 3/20/2022 then shows nothing between that date and September 2016.
There’s over 400 emails between the two dates and read/unread makes no difference.
Do you know with which version it worked for you last time?
Seems similar to
As simple as it sounds, have you tried sorting the inbox by something other than date and then back to date again?