30 PSI is more than plenty. My siphon feed Badger 200NH which is similar, paints perfectly at 15-20 PSI and will actually draw paint at even lower air pressure. That leaves a few questions.
Is the air working? i.e. is a powerful blast of air coming out the tip?
Are you thinning enough? The paint should be thinned to the consistency of 2% milk, which may require (depending upon the paint) a 2:1 or even 1:1 paint/thinner ratio.
Did you pull the trigger all the way back? Just as an extreme test.
Does the 150 have any sort of tip guard or cap that needs to be removed?
If you are using a siphon bottle (as opposed to an open top color-cup), is there a hole in the siphon cap to prevent vacuum lock?