Arrears nightmare

I'll try to make this brief. Had cs order established in Idaho in 2001. Ex wife signed for a "non-enforcement" order in 2003. She got remarried and didn't want a penny from me. So I didn't pay anything for 13 years. There was never a problem with me "owing" anything. This past year, she got on food stamps. Idaho started enforcing the order. I only found this out by checking my credit report on CKarma. And there was child support with a balance of over $36,000. WHAT ?!?! So I called Idaho cs and they confirmed this. They said just start making the minimum payment plus a few bucks and all is good. So I have been since Jan of this year. My case has been transferred to Alaska where I live now...owing $36,000 plus. I was NEVER informed in 13 years that this would continue to pile up and got surprised with this. The child is now 17 1/2. How can this be legal?????