Hello @Roger Roger ,
have you checked if the user has Microsoft Bookings enabled?
- Go to the Microsoft 365 admin center, then select Users > Active users.
- Select the desired user, then select Licenses and Apps.
- Expand Apps and check the checkbox for Microsoft Bookings.
Also, is MS Booking enabled for your organization?
- Sign in to the Microsoft 365 admin center as a global admin.
- In the admin center, go to Settings > Org settings.
- Select the checkbox for Allow your organization to use Bookings to enable or disable Bookings for your organization.
According to the MS documentation, O365 E5 is sufficient to access MS Bookings.
Hope it helps and don't forget to upvote.