That sounds like a frustrating situation. It's understandable to feel concerned if a casino asks for Know Your Customer (KYC) verification after winning an amount above the usual threshold.
Exactly and most importantly if the KYC threshold is covered in the T&C of the casino and this can be of importance for the gambler to take note of that requirement and be willing to pass through the KYC process if the player has gone through the KYC process but the casino denied the player his withdrawal still it then clear that that is a case of clear scam attempt and should be reported at will.
Many and most of the accusations that have spring up in recent time here have been majorly about kyc and what it demand and process have been, and it looks as if some scam casinos are using the kyc process to steal from players by not allowing them to withdraw even though they pass the kyc process.