Like it says, I’m getting the Cannot detect any Primary Machine error on all of my client devices. I’ve allowed the app through the firewall (Windows Defender); everything is on the same subnet, network segment, and gateway; I’ve uninstalled and reinstalled both the server and clients; I do not have a VPN running.
It was running just a few weeks ago, flawlessly in fact. The only thing I can think of that was updated was the Nvidia graphics driver, and maybe some Windows updates?
To verify if the discovery issue is on android viewer app, could you please try to connect using HTML5 Viewer on your non working devices (e.g. Pixel 3).
Just open a web browser (e.g. google chrome) then go to http://viewer.spacedesk.net/, then type the IP address of your primary machine to connect.
Looking forward to your feedback.