what could cause no water to come from any of the hot water taps?

Â Assuming you have a traditional gas or electric tank water heater and the inlet cold water valve into the tank is actually open, the hot water line might have gotten air-locked. You can try to fix it by opening all the taps and faucets in the house (hot and cold) starting with the highest, furthers away from the heater (just ask your family and see who complains about hot water most, them start with their bathroom :) ) and going down to the lowest floor. It may take 10-15 minutes and you will definitely run out of hot water but when you can see all the faucets discharging hot water evenly, you can close them in the reverse order.

You could alsoÂ flush the hot water lines with cold water by (carefully!) using one of the top floor mixing faucets. Fully open hot water valve (assuming no hot water comes out or the flow is intermittent) and take a piece of cloth and block the faucet, then turn cold water fully on. When it becomes impossible to block any of the cold watter spilling out of the faucet despite your best efforts, it's a good sign to stop the exercise. By now it's either worked or not.

If flushing didn't work, your next step is to call a professional plumber and have him check the hot line, most likely drain the heater to remove the sediment or other possible blockage.