Random child support question!!

So my husband pays child support for his little boy (every month we have never missed) despite the fact the mother took the little boy and said its me or your wife about two years ago. Anyways. Now she has moved from where the CS was previously being sent and we can't find her to get it to her by mail, the state, nothing. She ignores all calls and texts. Can we get in trouble for not paying if she is refusing it? And yes she has recieved several voice, written letter and written texts stating that we need to have her info to get it to her & the phone number is still the same for her. I am just confused because it's free money and why would she not want it!