Thank you... realized after post probably not enough info.. I have price pfister, single faucet... this is stand alone shower.. tub in bathroom works fine.. this was not a gradual occurrence... worked fine first shower yesterday, then no hot water second shower an hour later... I have taken off the handle, but can't seem to get the plate off... not sure what to do if I get the plate off but have been reading different posts and am wondering if this could be a mixer problem...

Thank you...realized after post probably not enough info..I have price pfister, single faucet...this is stand alone shower..tub in bathroom works fine..this was not a gradual occurrence...worked fine first shower yesterday, then no hot water second shower an hour later...I have taken off the handle, but can't seem to get the plate off...not sure what to do if I get the plate off but have been reading different posts and am wondering if this could be a mixer problem...
Broil water in a big pot and after is really hot add some cold water and check if you like it colder or hotter

Post your additions as an answer to your original, hard to put new info w/ the old.

The sleeve screws on to hold the trim plate down. You may have debris in the valve. Flush it out and rinse the cartridge.