Due to Child Support?????

Today, i called IRS and the Rep told me the reason why i did not received the direct deposit. The reason: My stimulus check was offset due to past-due child support. I do not even know how i owed the child support. I am 51, my wife passed away last year (mid of 2019) and i did not get remarried this year. We file jointly for 2019, we have a child who he is 26 years old and he is a master student in the college. He is dependent child of us.

Anyone can tell me how I owed the child support.