no hot water in the shower

Did they have hot water before? Who did hte plumbing? Could be a defective or improperly installed faucet. I can't see it from here so I don't know what was done, but I'd get the installer back.

Double-check the shutoff valves. Look for access panels in the wall behind the shower and work your way to the basement. You can narrow your search by determining if the sink by the shower has hot water.

I agree with Edwin, the installer is going to be the person that can best fix this problem. It may be simple like the installer forgot to open the hot water valve leading to the shower. Or it might be a symptom of a bigger problem like maybe the water heater? Do you have hot water in other areas of the house?

Mike

The cartridge in your tap is in backwards.

How long ago was it installed? Was it done by a professional who offers some sort of guarantee on his work?

Or clogged with solder from inside the pipe due to a crappy solder job. Safe to say that the cartridge needs attention. In a single handle pressure balanced faucet, the water should not run at all if pressure to either the hot or cold is lost so I think the regulator is stuck from debris.

Remove the handle and then the cartridge. Turn on the hot and cold water supply briefly to flush the new popes into the shower stall. Rinse and inspect the cartridge and replace. If that does not do it, call the manufacturer of the faucet and get a new cartridge under warranty.