if your phone screen is lit up, you will get no notifications on your watch.
sometimes things just get a bit wonky.
you can try unpairing and re-pairing the watch.
It should backup as part of the unpair, you can restore from that backup when you re-pair, So you shouldn't loose anything.
This will take a bit of time, and you'll want to have wi-fi. I've left mine on the charger the couple times i had to do this.
Disabling bluetooth on your phone (from settings, not control center) when the restore starts might make it go faster, as long as your watch can connect to your home wifi.