I have a faucet with a arm that you turn left ant right to get hot and cold water. For some reason I can't get any hot water when I turn the arm to the hot side. Checked all connections and the water is on... any suggestions?

How often do you flush your water heater? Sounds like some debris got into the cartridge and is now blocking the cartridge inlet ports. The solution is to shut the water off to the faucet and open it up. Remove the cartridge and check a clean the inlet ports. Now turn the water on for a minute to flush out the supply. Reassemble and test. Good luck, Tom

Do as Tom said. Also, look under the sink and inspect water supply connectors for kinks. If kinked, straighten it out. That will restore water flow.

Milo