Hi @Molly Wiltshire
Could you please tell me:
Does this problem only occur in the Teams desktop client?
Are you using New Teams instead of Teams Classic?
If you are using Teams Classic, please switch to New Teams and update to the latest version. Sometimes, failure to update in time will cause unknown errors in Teams.
If this problem only occurs in the Teams desktop client, you can try clearing the Teams desktop client cache instead of the browser cache:
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.