Additional meeting and call-related features and issues within Microsoft Teams for business
Dear Hannah,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
According to your description, it seems this issue is related to verification of authenticate. Regarding this point, this might related to MFA( Multi-factor Authentication had beef enabled. We need to confirm with you that whether you are using Microsoft 365 business/education subscription. If so, please contact the admin in your organization and refer Set up multifactor authentication for users - Microsoft 365 admin | Microsoft Docs to disable MFA and check if there is any improvement.
Sincerely,
Tommy | Microsoft Community Moderator