I have problem to access on Microsoft Teams in my organisation with Fortgate install but finally I found the solution
Go on Security Profiles >Application control
1-Allow Microsoft Teams (All features)
Go on Security Profiles >Web Filter >FortiGuard Category base filter >Bandwidth Consuming
1-Allow/Monitor Internet telephony
2-Allow/Monitor File sharing and software download (if necessary) "this can help you access to all Drive sharing if it's allow on Application control"