cal.com requires a one-time tenant-wide admin consent to function, as the tenant is configured to restrict users from consenting to third-party applications.
1. Log in to the Microsoft Entra admin center as a Global Administrator or Application Administrator.
2.Navigate to Identity > Applications > Enterprise applications.
3.Search for cal.com.
Note: If the app is not listed, ask one user to attempt the sign-in flow once. This will trigger the creation of the Enterprise App object in your directory, even if the login fails.
4.Select the cal.com application and go to Permissions in the left menu.
5.Click the blue button: Grant admin consent for [Organization Name].
6.Accept the permissions (strictly limited to Calendars.Read, Calendars.ReadWrite, User.Read, and offline_access).