Why does my Apple Watch 8 not track my wrist temperature?

However, for reference, some possible reasons why an Apple Watch may not be tracking wrist temperature include the following:

1. Wrist temperature tracking may not be a feature on the specific model of the Apple Watch.
2. The feature may be disabled in the watch's settings.
3. The watch may not be worn tightly enough on the wrist for the temperature sensor to function properly.
4. The watch may not have been in contact with the skin for long enough to provide an accurate temperature reading.
5. The temperature tracking feature may be affected by environmental factors, such as extreme cold or heat.

If it is saying more data needed then at least it is "working on it"

Start diagnosis by force restarting the Watch and paired iPhone at the same time:-

Force restart the Watch

i.e. press and hold both the side button and Digital Crown for at least 10 seconds, then release both buttons when you see the Apple logo. Then while Watch is restarting,

Force Restart the paired iphone   Force restart iPhone – Apple Support (UK) 

If nothing happens inside another week reach out to Apple Support Click here > Contact - Official Apple Support  or phone numbers  Click here > Contact Apple for support and service - Apple Support   or Click here > Genius Bar Reservation and Apple Support Options - Apple 

How many nights has it been running?

Sleep Focus must be enabled for at least 4 hours a night for about 5 nights.

While your baseline is being established, you'll see "Needs More Data" at the top of your chart. What does it say?

The rest of the diagnostics is here

Apple Watch basic diagnostics - Apple Community

Check

iPhone, Watch app, My Watch tab, Health that all your data is in there correctly.

iPhone, Watch app, My Watch tab, Privacy, that Fitness tracking is turned on