Mr.Nice

It's not about stamp or any other issues with your paperwork. It's about refusal to pay the balance. Consider filing claim via any of ADR services and later escalate to Curacao court. Not easy way and not fast but worth try. Of course provided you are a real person and all fine with your IDs and address. They will not accept anything from you - it's just a legal way to drag the time and not to pay. Fortunately I never encountered this on Stake but other online casinos a lot of times.