I'm assuming that it's stock and it's using a stock pump. It's most likely dried out. But to be sure put your thumb over the air release and pump it. If it starts to pump then you need to flush out any gunk that could be in your dump valve. And if it is a dried pump, just replace it with a spalding ball pump from wal-mart.
They're only about 5 bucks. And turn your 10 ish pump big blast. Into a 2 pump one.