with the latest update to Supernova (v115.2) it occurs now that if you open a mailbox or subfolder from your account that the display does _not_ update to see the latest incoming messages which got pulled just right away.
But this was the case with any previous Thunderbird edition _before_ Supernova and was very useful, too! 😉
Currently you need to try to scroll down in the message-list if there might be any _new_ messages there which you haven't seen yet/since the last check.
Maybe you wanna change this back to "how it used to be" with "non-Supernova"-versions of thunderbird again.
Thanks a lot in advance and all the best for all your future and very appreciated work,