I'm not familiar with this particular model of camera as I own a trailer but I did have the same issue once. On mine, the length of time that I held down the power button on the mirror made it cycle through four picture orientations.
Foe example: (Right side up, left right normal), (right side up, picture reversed), (upside down, left right normal), and finally (upside down, picture reversed).
I had to hold down my power button until it cycled to the correct view. Now I never touch the power button and let it turn on automatically when my vehicle starts and powers on my accessories.
I don't know if this helps but it is something to try. None of this was covered in any documentation but I've owned enough Chinese made electronics to know that any single button or switch usually does many things. Good luck!
This may be your manual -
Page 14 shows the rotate image solution.