It sound like the tank is in winter mode has has no water in it.
While the heater has been off for some time the make sure it is cool pull the tab on the safety valve at the top of the heater. If no water comes out the heater is empty and you need to change the postion of the bypass valve. When you do this and are attached to city water or the pump is on you will hear the tank filling. Let it fill for several minutes and then open a hot water faucet to bleed off air in the tank and allow more water in. Do this until you are not getting air at the faucet.
NEVER light a hot water heater until you know there is water in it. It is called a bomb waiting to go off as there will be some water in the bottom of the tank and as soon as you convert that to steam it will blow, hopefully through the safety but no Guarantee.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles