When turning on the shower faucet there is no hot water.

change the cartridge

If I understand correctly, you have single handled shower faucet.
Normally there is a wait for hot water to arrive at faucet.
But now hot water is already at shower faucet.

Single handled faucets have a mixing area inside valve where hot and cold come together before going into sink.
This mixing valve can have crossover where the hot and cold can pass through to each other even when faucet handle is off. When single handle faucets get old, this can happen.
How it happens:
For example another faucet is turned on inside house, and pressure differential between hot and cold causes hot water at shower handle to pass through mixing area and into cold water line.
So if another faucet has been run, then that lets hot flow to faulty single handled shower faucet.
To confirm this is the problem: turn on other faucet and put ear against shower faucet to listen for moving water.
This condition may also signal there is a water leak.
The problem is not harmful, but will draw cold water into water heater each time, and is energy wasteful.
Replace faucet or have plumber repair problem.

u need to adjust the scald protector all single handle units are shipped in cold position for safety reasons if have paper work for handle it explains how to adjust if not unscrew handle and remove on handle / valve stem will see a red and a blue plastic clips pull back clips and turn slightly and push back do this till desired hot and cold setting are to your liking replace handle and your done

Can you remove handle , behind handle there should be a dial to move to increase hot or cold supply.

Remember where you start and remove it and replace a 1/8 to 1/4 turn counter clockwise, just put handle on try it and see if it changes and adjust accordingly.

IS THIS A SHOWER ONLY? IF SO ,I WOULD REMOVE THE SHOWER HEAD FIRST THEN TURN YOUR WATER ON.THE HEAD JUST MIGHT NEED TO BE CLEANED AFTER 11 YEARS.

First try adjusting the pressure balancing gear located right behind the handle. If you still do not have hot water I suggest to replace the cartridge.

You can try to rotate the first plastic ring to the left of center a few teeth, this will let the handle advance alittle more to the hot side.

Try draining the system and apply air pressure (min 30psi) to each faucet. Open other hot water faucets to allow pressure to vent. Next try draining and cleaning the hot water tank.

change the cartridge it is bad or defective.

tun off the water.
unscrew teh allen screw under neath the handle. pull out hteh handle. undo the wall plate and gain access to the cartridge in the handle body. turn the artridge around 180 degree and reisntall all parts.