Hot water stopped working in shower

[southofmotown]

My shower stopped putting out hot water. I thought it was the cartridge, but that looks fine. Behind the cartridge there is no water even coming out the hot side. I blew through the shower head with compressed air and then plugged the shower head and ran the water, thinking that might shake something up. No change. It is just a shower with no tub. There’s a single handle for controlling the temperature and flow of water. Thank u for any suggestions on how I can get hot water back!

 

[breplum]

If your water heater cold supply is on and you have hot water everywhere else AND if you don't have galvanized pipe, I am afraid that it is just a matter of working backward and replacing pipe.
If you have galv. steel pipe, then of course it is obsolete mtl. and clogged
You will either have to learn all about water re-piping or call a plumber for help.