Unless I’ve specified the accounts from the Trusted Domain in my NPS server, those users were still not able to be access my Network.
Event Log ID 6274, Audit Failed
The Network Policy Server was unable to connect to a domain controller in the domain where the account is located. Because of this, authentication and authorization for the RADIUS request could not be performed.
I had to register my NPS server in the other Domain too by adding it in the RAS and IAS Servers group.