For further analysis, could you please run spacedesk Driver Console window on your primary machine (just click the spacedesk tray icon on the task bar) then click Diagnostics -> Save All Information button then send us all the diagnostic logs.
PS: Saving all information will take a few seconds, then please send us the whole folder which contains all the diagnostic logs collected.
Please right-click the folder -> Send to -> Compressed (zipped) folder, then attach the *.zip file on your next reply.
Please also tell us the info on you secondary machine.
What is the operating system?
Which spacedesk viewer app did you use? Android/iOS/Windows10/Windows7/HTML5?