Exchange 2013 ECP: All fields are empty

Hello,

I'm using Exchange 2013 CU21, I'm able to login normally to ECP, all major properties are working but I can't change anything because all fields are null (empty)

Example: ECP --> Servers --> Virtual Directories --> OWA --> when trying to change OWA settings, all fields are empty in the OWA pop-up and I can't navigate OWA pop-up fields

The above is happening in all pop-ups, I used IE11 and Firefox, same results,

Any help please?

Thank you