Resting and walking heart rate not showing on Apple Watch Series 9

Did you already try to force restart your iPhone and Apple Watch?

This should trigger a new sync of your data between the watch and the Health App.

Force restart iPhone - Apple Support

To force restart your watch, press and hold the Digital Crown and the Side button together for about 10sec, until the Apple logo comes back again.

Is your Apple Watch still listed as a source in the HealthApp on your iPhone in HealthApp/Browse/Heart/Today->scroll down the screen,

->Data Sources & Access ->Name of your Apple Watch

Can you see any data from previous days in the same section under:

->Show All Data?