I just can't handle it

I need an assessment from people who are familiar with family law, maintenance or similar situations. I have a son from a previous relationship. The child's mother has been blocking all contact between me and my son since 2018. I haven't seen him since 2018. I haven't received any information about him either, although I've asked several times. Now the responsible maintenance office is demanding several thousand euros in maintenance arrears from me. Just ago