Hello,
I did a fresh ArvcGIS Portal installation on a server. Site creation is successfully completed and I can login to the portal with portal admin user. But I am not able to use portaladmin.
When I go to "https://portal.host.machine:7443/arcgis/portaladmin/" I see the login screen , and I can successfully login to the portal and see below screen.

Problem starts here. I am not able to enter any admin menu. Whenever I click any of the link on admin portal, it take me out to the login screen again.

Do you have any idea to solve the problem?
Thanks.
Suleyman.