Hi Svein
Certainly try a restart and - if that doesn't work - a force restart of your Apple Watch first:
Restart: Press and hold the side button until you see the Power Off slider; Drag the slider to turn off completely; Afterwards, press and hold the side button until you see the Apple logo.
Force restart: press and hold both the side button and Digital Crown for at least 10 seconds, until you see the Apple logo.
Restart your Apple Watch - Apple Support
Also restart your iPhone.
If you find that neither of those work, then you can unpair and re-pair your watch and iPhone, choosing to restore from the Apple Watch backup on your iPhone when prompted during the set up process. Content is backed up automatically and includes most data and settings (see the exclusions here: Back up your Apple Watch - Apple Support)
Unpair your Apple Watch and iPhone - Apple Support
Set up your Apple Watch - Apple Support