My name is***** am sorry to hear that you are having this issue.
I will be glad to assist you with this.
The auto-rotation setting may be locked in one position. Here’s how to unlock it:
Step 1:With the Cover detached, swipe in from the right edge of the screen, or select Action center in the taskbar.
Step 2:If Rotation lock is undimmed, auto-rotation is locked. Select Rotation lock to unlock auto-rotation.
Rotation lock is undimmed when auto-rotation is locked. When auto-rotation is locked, the screen won’t rotate when you change the orientation of your Surface.
Reattach your Surface Typing Cover, fold it back, and check to see if the display rotates automatically when you turn your Surface.
If auto-rotation still isn't working after you unlock auto-rotation please let me know.