Apple Watch Series 2 not adjusting brightness

Hi All

I have had the apple watch series 2 for a number of years and found that it occasionally stops adjusting the brightness to ambient light and instead uses the full brightness all the time.

Unfortunately in the last few weeks this has gone from an occasional issue to permanently displaying information at full brightness. Adjusting brightness in both the phone app and on the watch does nothing.

I've reset and re-paired the watch several times and am out of ideas.

Has anyone else had this issue and know how to fix it?

Thanks

Jamie