Hi @lior2df,
Please check in spacedesk Driver Console -> Diagnostics -> Incompatible Software Products, for any Incompatible software product present in your primary machine that might cause the Display Off issue.
As for the tearing and black screen, on which screen is it happening?
In the spacedesk Viewer app screen? Or in your Windows main monitor?
By the way, if your old tablet is Android or iOS, please also try connecting via USB cable.
Just enable the USB Cable Android/iOS in the spacedesk Driver Console -> Communication Interface.