In my extra bathroom I cannot get hot water in the shower. The bathroom sink has hot water and I turned the valve under the sink. The facuet also shuts off when you turn it all the way to the hot section. Any suggestions?

Which faucet turns off on hot, the sink or the shower? If the shower I'd say you have a completely clogged hot inlet port on the shower mixing valve. Remove, clean and reinstall after greasing with silicone jel.