Please make sure that you have the most recent spacedesk Driver version from the website https://www.spacedesk.net.
You can easily verify if spacedesk SERVER is installed correctly via:
– search for spacedesk Driver Console, open the window and check if spacedesk status is ON
– run services.msc, find spacedeskService if status is Running
For assistance, please check Setup Primary Machine -> Verify is Setup was Successful chapter in the user manual https://www.spacedesk.net/user-manual/#item_448.