Had breaker to elecric heater turned off for couple months after turning back on the cold water works but there is no water at all coming out of hot side. There;s only one valve and its turned on what is the problem?

Are you saying that you have no hot water coming out of any faucet only cold or are you saying that you have no hot water coming out of the heater? When you touch the pipe feeding the house , on the heater, is it warm or hot? Back to you, Tom