FJ as a sportsbook had every right to cancel any match for any reason do long as they do it before it starts. You are not entitled to something because of it - had they done it when the game started or afterwards then you'd have a case here but as of now there is nothing. Bet was canceled BEFORE it was being played, what happened after matters not.
Of course they can theoretically cancel a bet in advance, but they need to justify it with a valid reason; otherwise, they cannot just randomly cancel a bet in advance for no reason AFTER a user has already placed the bet. And in this case, their reasoning is completely wrong and invalid because their explanation is simply not true.
They claim that they did it because of a change of odds from 2.6 to 1.7, but 1.7 never happened and you can verify this with a site like oddsportal.
And now they can't just make something else up because it goes against their original explanation, so they should simply take responsibility for posting De Jong above 2.6 odds for several hours the day before, and anyone who bet on him to win at these odds should be rewarded for it. Fair & simple.
Fair and simple.. For you?
Perhaps we should also look into anyone who placed a bet on the opposite result and retroactively take btc from their accounts to fund your "fair and simple win". That'll make sense right and it would be fair and simple to them too, right?