Early in the day or hot water worked just fine, showers were taken and clothes washed but just a little while ago my wife was going to bed and went to wash her hands and she told me there was no hot water in either of the bathrooms. I checked downstairs and the kitchen sink nor any other faucet was producing any water from the hot side.

What could be causing this issue?

There are only 2 reasons water won't flow - supply valve to heater is turned off or blocked or outlet from tank is plugged. If you have older style heat trap nipples with the ball check valve they can sometimes stick shut or get plugged if a dip tube is deteriorating . Turn on a tub faucet and gently hit the hot side nipple with a small hammer or wrench to see if it will open. You can check the supply by carefully opening the drain valve. Let us know what you find out.