It seems like your solidworks model is not fully defined/connected. This allows the model to move. Under normal circumstances an error should be raised instead.
But what is the problem here (I'm having to guess a bit). Your follower-coodinate-systems of your revolute joints are most likely not in the same plane. To fix this you have to use a "Rigid Transform"-Block on one side of the "Common Gear Constraint". In there you have to put the offset of the two coordinate frames.
