A user in my anization/tenant has a MSFT Fabric (Free) license associated when seen in the M365 admin center/MSFT Entra ID:

But when that user is trying to login within app.powerbi, that person is getting the below aspect :

Asking to start Fabric Free Trial capacity and when clicking on it getting the error:

Note: The user is able to get PPU capacity but not the Trial capacity when creating the workspace

what is the cause? Note: we also checked the region belongs in the region supported under Trial capacity