Your are trying to drain it from the bottom of the tank, right?
Often times if no one ever drained some of the sediment out of the bottom every year like your suppost to there's a layer of sediment on the bottom.
Sometimes a metal coat hanger can clean it out enough to get it flowing.
Some have been so pluged up I've had to use an appliance cart to get them outside still full.
If I go to all that trouble I remove the cheap valve that came with it and replace it with a bronze nipple and a ball valve with a garden hose adaptor.
Often times if no one ever drained some of the sediment out of the bottom every year like your suppost to there's a layer of sediment on the bottom.
Sometimes a metal coat hanger can clean it out enough to get it flowing.
Some have been so pluged up I've had to use an appliance cart to get them outside still full.
If I go to all that trouble I remove the cheap valve that came with it and replace it with a bronze nipple and a ball valve with a garden hose adaptor.