Just because we haven't seen it, doesn't mean they haven't.
Pence hasn't actually done anything wrong. His role is not to decide a vote unless the House and Senate cannot make a decision. So far, both House and Senate have come to a conclusion without need for intervention.
So far, he is just doing his job President of Congress.
Not saying he isn't guilty of other things but in this case, he hasn't done anything wrong…yet.