Would the child support be null and void if the non-custodial parent died or gave up the parental rights?

I gained custody of my daughter on January 20, 2013 and have not received any child support. But Texas child support has been trying to get the mother to pay. I call every month to the child support department in Texas. This month they stated that they are working on something they found which could cause the child support case to close or get a lump sum payment that it could go either way and the Court order from January 20, 2013 would be null and void. My ex wife has a criminal record and has been addicted to pain killers in past so I am guessing that either she passed away or gave up parental rights some how. My daughter and I do not have any contact with her and only contact we do have is with my ex wife's mother and she states she does not have any contact with her daughter because of bad issues between them and her daughters drug use. So my question is: are my assumptions correct on reason why they would cancel child support and/or pay a lump sum? Would the non-custodial parent be passed away or given up custody to cause that the child support order be null and void ?