if your tubes are showing large amounts of air. then the first thing to check is if your ink has run out. air can also get into the ink lines if the damper has an air leak at the o-rings. the way to check this is take off the damper. with a syringe pull ink back into the damper. leave it hanging (not plugged in) for several minutes. observe the ink level int the damper when you do the syringe. and then see if the level goes down. re-tighten the compression fittings on the dampers to be very solid. when rotating the dampers to plug them back in be careful not to re-loosen them.
is it just the one damper that is missing ink? or you mentioned "all damper" are out of ink. this is a rare thing to have them all loose vacuum at once. it is usually an isolated event at a certain head.
this is an easy problem to diagnose. you should have your printer working perfectly very soon.