Lol, that’s not the explanation then!
Sorry, I don’t have any more bright ideas. Unless you switched from one type of S1 to another? But I thought most types of S1 automatically covered dependents.
The letter that CPAM ask for is quite a standard end of rights letter. When we arrived we were asked to provide one before we would be accepted onto CPAM’s books. But that was to be accepted into the French Health system in our own right, not via an S1. So perhaps since your children were born here the the French system thinks they should be treated differently?
Personally I would challenge the DWP about not supplying an S1 for dependent children. Is your S1 as a result of your husband’s? (Or vice versa) . If so, what’s the difference!!