Finnair is notoriously bad to honor the EU261 rules, slow to pay, or not paying, it's a calculated strategy from their side. There are companies that will take a cut of your money that will process the request on your behalf, as they have lawyers to threaten Finnair the payment success is higher.
In i similar way I threatened Cathay to take them to the small claims court citing a reference case under global aviation practices that Cathay has signed up to, after this type of threat I was suddenly paid the full amount instead of a partial payment for my broken luggage. Again this is strategy from their side to try to make us accept lower compensation.