I use VNC all the time on my Pi but sometimes when I have a long running task, I walk away. When I get back "Cannot currently show the desktop" is shown on the screen. I know the computer is still running OK. I just cannot bring up the VNC virtual screen on a client on my PC...
Any thoughts on how to get the virtual display working again or to restart the server without killing the current activity? A reboot always work, but then I need to restart my long running task.