RDP into Zorin18 when remote PC requires login

Just updated all my computers to Zorin18, and testing out remote access via RDP using ThinCast.

RDP works fine when I've logged into my remote PC, but after a while the remote PC returns to lock screen (user not logged out, but I have to re-authenticate to access desktop), and then Thincast will report remote PC not available.

I figured this required me to go into the remote PC's settings and enable Remote Login, not just Desktop sharing. When I do that, Thincast will connect to the remote PC, but all I see is a black screen in ThinCast.

Can anyone explain what I need to do to get RDP working on a remote PC when not logged into the remote PC?

you can try this :
Disable automatic screen lock
On the remote PC (Zorin 18):

Open Settings → Lock screen → Disable “Lock screen after”.

Or via terminal:

gsettings set org.gnome.desktop.screensaver lock-enabled false