Error when validate settings in Report servers by any admin account which is not account used to install the AX reporting services extensions.

First thing you need to verify the Service account and Execution Account are properly configured under Reporting Services Configuration Manager.

After some troubleshooting, I found UAC was not turned off. I was running on MS Windows Server 2012.

UAC has to be turned off via registry by changing the DWORD "EnableLUA" from 1 to 0 in "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system". You will get a notification that a reboot is required. After the reboot, UAC is disabled.

After UAC is disabled, the issue is resolved.

social.technet.microsoft.com/.../13953.windows-server-2012-deactivating-uac.aspx