SE watch

First, check if this is actually enabled.

On your Watch, open Settings and go to Display & Brightness > Wake on Wrist Raise - make sure that's turned on.

Try turning it off and on again for good measure.

Also, I'm not entirely sure how the Watch detects someone raising their wrist, but it might have something to do with your height, so make sure that's up to date.

That is theatre mode,swipe up on the watch face to turn it off;