You need to give them more time I think.

In the past, Vueling has always been very bad at paying compensation, so going through an agency was almost the only way to get something. But since their operational meltdown a few weeks ago they seem to have become a lot more willing to pay up. (It seems to have been one of the promises that they made to the Catalan government and their customers about how they would behave better in the future...) But they probably have an enormous back log getting all request processed since the start of summer.