Hi
Operation of the Digital Crown can be affected by substances like dust or lotion. If it has stopped operating as expected, then it may help to clean it by following the steps here:
Use the Digital Crown on your Apple Watch - Apple Support
It may also help to restart your Apple Watch (if necessary, by force restarting it):
Restart your Apple Watch - Apple Support
If the issue persists, then your Apple Watch may require service. Contact Apple Support (mail-in service may be available, if required), make a Genius Bar reservation or visit an Apple Authorised Service Provider with a view to arranging for your Apple Watch to be inspected and, if recommended, serviced: