Error 503 service unavailable Exchange dashboard

Good morning,

I have installed Exchange 2019 (Cumulative Update 7) on a Windows Server 2019 Datacenter.

All preliminary activities went right (installing .Net, installing Microsoft Unified Communication Managed API, preparing AD, ecc.).

Of course WIndows Server 2019 hosting Exchange is domain joined.

I have launched Exchange setup and procedure ended with no errors or warnings: all seemed fine.

When I try to access Exchange Administration console (ECP) I got: error 503 service unavailable.

What can I check?

If need other details, please ask.

Thank you in advance.

Best regards.

Marco