Here's the problem: we just finished a major tile repair in our master bathroom shower. The shower was not used for several months. Both sinks in the bathroom work fine with hot/cold water. However, we are getting no hotwater in the shower (single handle) and the bathtub is getting neither hot nor cold water (actually the tub is 2 handle faucet and I can hear the cold water trying to come, it will dribble a bit then stop - nothing on the hot). What is going on? The plumber that built the house put some kind of return/circulator on the hot water in the master shower so we would get hot water right away. Is there some kind of air lock from having not used the shower? Why doesn't the tub work? (no aerator on tub faucet). Thanks!

Your best bet is to call the plumber back and have him to recheck his installation.

In the interim: what kind/type/brand of faucets did he install ?

Moen faucets -
But it seems to more a problem with the lines not the faucets? Is it possible to get an air lock from non-use? Is there a "way" to prime the flow?

I would clean the cartridge. Chances are there is debris inside.

Moen faucets -
but it seems to more a problem with the lines not the faucets? Is it possible to get an air lock from non-use? Is there a "way" to prime the flow?

For openers there's no such thing as a air lock in a pressured water system.
Any air in the system gets pushed by the water pressure. Follow Milos advice and let us know how you make out. Good luck. Tom