Maybe there are still platforms, forums where there is their representative and he is active?I wrote a review on Trustpilot.
Coinplay casino already has a bad rep on this forum and their representative is no longer active here, so you will hardly get any response. But, although I cannot guarantee results, there are some steps you can take. Firstly, try posting your complaint on websites like AskGamblers or Casino.guru. They have a reputation for assisting gamblers facing issues with gambling sites, and you might get more responses there. Coinplay casino has a few unresolved complaints already, but even if you do not get a resolution or response, at least you can warn the wider gambling community and potentially lower their score on those platforms.