We’ve faced a problem logging on to Wndows 2012 R2 servers via RDP recently.
The User Profile Service service failed the sign-in.
User profile cannot be loaded.
Fix: Go to \\problematic_server\C$ from another server
Open Security tab in properties of “\Users\Default” -> Advanced -> Change Permissions -> tick checkbox “Replace all child object permissions with inheritable permissions from this object” and apply changes.
You should be able to log in now.