User without local admin rights can't connect to Win8 PC via RDP

We have a user that until recently had local admin rights on his Win10 PC. He needs to connect to a Win8 VM on Azure via Remote Deskop. This worked fine until we had to remove his local admin rights.

Now he always gets a 0x80004005 Authentication error if he tries to connect. If we run RDP as an admin it works again.

Any idea why this happens?

Local admin accounts include the ability to connect via RDP. To give the user rights to RDP without full admin rights, add them to the local "Remote Desktop Users" group from the system in question.

Click Start and type "compmgmt.msc" Expand "Local Users and Groups" Click Groups and then double-click "Remote Desktop Users" on the right Add the users account (remember to add from the domain, rather than the local system, if this is a domain environment.)