skimmer stopped producing bubbles

what should i do to get the protein skimmer to produce bubbles again? i blow into its air tube and bubbles start up, but when i stop, the bubbles stop

 

is there maybe an obstruction in the line , that when you blow it clears for a bit and then resettles? or is the water in your sump too low in relation to the pump?

 

i fixed it, i sucked water threw a bunch of times before it reached my mouth, after doing that several times i blew air in it and it continued producing bubbles

 

good work reefer

 

My 4 week old Red Sea did the same thing, after several blow throughs like the poster above, I could never get the bubbles produced again. Red Sea sent another pump out. And yes, no obstructions, only when I turned it off, it stopped.

Vic