Hi ,
The participants will always see what your camera sees. The Mirror video option only changes your personal view of your camera, not what your camera is sending to the otherparticipants.
Hold up something with text on to camera and ask yourparticipants if they can read it. Chances are they can, and that they are receiving your video correctly.
The Mirror video option is just a personal preference of how you want to see yourself at your end - whether you want a mirror-like image or not.
If your camera is presenting a flipped image into Zoom, you may need to check your camera driver settings. But do a simple visual check with anotherparticipant first.
What camera are you using?
Hope this helps.
Rupert