Ex avoids CSA with fraudulent documents and nothing is done about it

I tried getting child support from my sons dad when I lived  in London 2002-2013. But even though he was working  I always got a reply back saying he owes 0. This was because he would use different ni numbers I was to find out. They had his name dob and address but still wasn’t enough. I then moved to Denmark and the government here tried to find to pay child support through them but again nothing. I wonder if the csa has gotten any better with con artist like him ? He’s never paid anything , he’s a fraudulent person on other things . Fake passport etc. I did let the police and court system know when I went to court to be allowed to take my son to Denmark. But they never did anything . He’s always had access to my son but never done anything about it. How he can get away with not paying for a child for over 15 years is mind boggling.