Hello, Greg
I am Igor and I will be glad to help you with this question :)
Check with some other Team just to exclude the possibility that there is some ongoing issue.
If the issue happens with only one team or channel, please try to clear cache from the Teams Desktop app by following steps below
https://www.uvm.edu/it/kb/article/clearing-team...
Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
If the issue persists, that can be an internal error and then I suggest you to ask your admin to open a support ticket on the 365 admin center.