Why has my Apple Watch 10 stopped tracking sleep?

Purchased apple watch 10 in Jan 2025. Last few days it has stopped recording any sleep information. I have restarted watch and also iphone. Still no tracking on sleep. It was working up until last few days. I wear my watch the same way I was wearing when it was tracking so It cannot be that. Any suggestions to fix. thanks.

[Re-Titled by Moderator]