CSA doesn’t class my case as a priority

Although my children are now 27 and 28 I have been informed by the CSA that their father owes me £16,000 in unpaid child maintenance! When I approached them years ago they told me I was not a priority case as I was working. They gave priority to single parents on benefits. They just kept giving me new case numbers so in the end I just gave up. I told them I do no want the arrears written off and asked if they would now pursue the case. Silly Question! I have about as much chance of seeing a penny of that for my girls as flying to the moon on a broomstick. It’s appalling.