Is it on mirror mode when you connect your viewer app?
1. You can easily disable the auto-rotation from your viewer app settings -> Rotation, then uncheck the Auto-rotation, then you can connect again.
2. Another thing you should do is to clear the display settings in your primary machine before client connection.
Just click the spacedesk tray icon on your notification task bar, to open the spacedesk Server window, then click the "..." button to display a menu, then select "Clear All display Settings".
Please let us know if our suggestions helped.
Looking forward to your feedback.