Why is my Apple Watch not recording sleep data?

So just got series 10 watch and using with iphone 15 pro max.

Apple have remotely checked watch and say that all sensors are ok.

I followed the steps 100% but not working.

Sleep kicks in at correct time and goes into sleep mode (full charge on phone and watch).

alarms wakes me up but no data.

In fact two nights it showed light blue bars saying I was averaging 3 hours sleep.

When I checked the sleep data all of the data was showing -- (core, REM etc).

Also awake time was showing 100%

I went into genius bar (is it still called that) he confirmed I was doing everything correctly and was no reason why it should not work. We reset again and said I would take home and see if it worked, otherwise I would have to take it back in and they would send it away to try and replicate the fault.

I bought the watch for the specific reason of tracking lack of sleep.

I do have severe sleep apnoea and it does not even report this or any respiratory issues.

So my question is this. The guy in the genius bar confirmed that if I set sleep on the watch while I am awake, the watch should still detect something and I should see data. Is this true as I have also tried this and same result nothing.

I have reset watch a number of times and also the phone but still nothing.

Any one had same issue and eventually get it to work.

[Re-Titled by Moderator]