Hi @ant1dote,
Could you please open the Windows Display Settings on your primary machine and then check for detached/greyed-out client. if there is, just attach it by selecting extend from the drop-down menu.
You can also refer to our CONFIGURATION AND SETTINGS
-> Windows Driver (Primary Machine) -> Desktop Extension or Desktop Duplication (mirror) Settings in Display Control Panel chapter in our manual – https://manual.spacedesk.net/DesktopExtensionorDesktopDuplica.html