Hi
Degas everything.
Pop off the quick release hose, push on the collar and pull the hose,,,
Make sure the hose has a good clean cut on the end and is not damaged in any way.
Have a look in the collar. I have seen players pop it off in muddy conditions and clog the collar up with debris etc.
Make sure everything is clean and reassemble.
After that it may be a new elbow but they are good and cheap
Ed