Hello leadsan,
Thank you for reaching out Surface Community. It is possible the rotation sensor is disabled. Let's check Registry Editor. Follow the path below to check if SensorPresent File key was set to 0, change it to 1 and restart.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\AutoRotation\SensorPresent
If the issue persist, check Enable File if it is set to 0, change it to 1.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Autorotation\Enable
If this works, we highly encourage you to inform our Community by clicking on Yes or marking my post as an answer. This will help other members who may have the same issue as you. Otherwise, don't hesitate to update us so we can further assist you.
Regards,
KarenJune_F