If you are behind one month in support they can take someone to court for contempt.
I've known people they have chased down pretty consistently before it ever got that far. Everyone I know got a summons to appear in court after being late 90 days. That's when they usually go after you. However, I don't know if they did it on their own or if the CP stayed on their butt to get it done.
It is possible to that she is avoiding getting served to come to court and hiding out which they can't do anything about. They try to locate these people to have their wages garnished, which I'm assuming she is having hers withheld or is under order to do so. She must be getting paid under the table IF she is working because they would have given you her tax returns by now also.
If you're going through CSE, you're probably just going to have to stay in touch with them.