Genie garage opener only opens when I give it a push, but closes fine!?

I have a Genie garage opener and when I push the on for it to open it'll make the noise, but the door doesn't go up. While its making the noise I have to walk to the door and help push it up for it to go. If I stop pushing the door it'll stop and just make the noise until I help it up again. Once its all the way up the noise will stop. When I push the on for it to go down it'll go down on its own. Anyone know why this is? Please help! Such a pain...