Digital Crown not depressing

Follow the steps in How to clean your Apple Watch

"Clean and dry the Digital Crown

If the Digital Crown gets stuck or won’t move, check for debris and wipe down your Apple Watch. If you find substances like dust or lotion around the Digital Crown, follow these steps to clean it, and repeat as needed:

1. Turn off your Apple Watch and remove it from the charger.
2. If you have a leather band, remove it from your Apple Watch.
3. Hold the Digital Crown under lightly running, warm, fresh water from a faucet for 10 to 15 seconds. Soaps and other cleaning products shouldn't be used.
4. Continuously turn and press the Digital Crown as water runs over the small gap between the crown and the housing. 
5. Dry your Apple Watch with an absorbent, non-abrasive, lint-free cloth. Be sure to wipe the surface of the Digital Crown, the space between the Digital Crown and the watch case, and the surrounding surfaces, removing any water."

Edit: If those steps do not work use the Contact Apple Support link as aptly suggested by MrHoffman.

Watch Repair

watch Service Pricing

Assuming the crown spins freely, and you’ve looked for and removed any visible debris wedged under the crown…

Contact Apple Support. Use the Get Support link in the upper right of this webpage.