Quote:
"Should you hold it the right way and the nozzle still doesn't release creamy whipped cream goodness, try running the can, but not the nozzle, under warm water. According to LEAFtv, the butterfat in the cream could have congealed together and is keeping the cream from moving toward the nozzle. Warm water should help loosen the butterfat. Another issue is a congested nozzle from leftover butterfat and sugar inside of the nozzle. To fix this, just turn the can upside down with the lid on in a cup of warm water for a few minutes. It should have the same effect as before and clear the nozzle's airways. Just wipe it off, give the can a good shake, and try using it again.
Whatever you do, don't push anything down inside of the nozzle because it could poke a hole in the valve."
Source:
https://www.mashed.com/301126/try-this-if-your-whipped-cream-nozzle-has-stopped-working