I've still got an open dispute from KLM back in 2018! Every month I get a brief update to say it is still ongoing:

> We’re contacting you about your claim for compensation for your KLM-Royal Dutch Airlines flight to Helsinki on 2018-09-11.

You should probably either take them to whatever your local equivalent of small claims court is, or use one of the "we enforce your rights but take 30%" portals.

If it’s any help, I eventually got mine. Just followed their online process. I’m in Canada. Didn’t get my refund from Air Transat (only a credit) and as long as the Canadian government allows this, I’ll probably be waiting at least another year to use the credit.

I'm guessing they won't come unless you chase it. Nothing happened to my refund for May flights until I called, after which the money came within a week.