Not able to log after gaining access to the remote computer user's screen on iMac 5k running High Si

My remote iMac 5K 8Gb ram High Sierra is online and activated with TV. I can log in up to the user menu interface, the mouse moves around but I can't click on any of the users thus not able select the user name and input the corresponding password. I can log in and log out from that screen but that's it. There is an option to Force Quit, and not an option to reboot. Since I'm able to go back and forth to the remote computer I assume the issue can be solve. The Force Quit is not an option since I won't be able to boot that computer again, I assume. Force Quit will shut down the remote iMac?

The same happens if I use my iPad to gain access to the iMac.

Sorry if I choose the wrong Board. I couldn't find one for Apple OS.