Well, I'm afraid we may have stumbled upon the problem. Having multiple accounts is against the rules of every casino and it's usually only discovered when you make a withdrawal. I'm sorry, but nothing is verified when you deposit, it's a voluntary action on the part of the player and the player is supposed to have studied the basic terms and conditions. I know how it sounds, but that's how it is.
Withdrawing money is really different. The casino has to verify that there were no violations of the rules, then verify the player and their identity, and only then can they send the money.
This almost looks like closing an account with multiple accounts.
BUT you are right that the message is quite nonsense without any further context that would explain very well why the casino wants it. Even if you were addicted and I am not saying that you are, no such document is a condition for a payout. It may be a condition for unblocking the account, but it is not related to the withdrawal. Feel free to show a screenshot of what the chat wrote to you or please try to remember everything he wrote to you.
It is important to know whether verification is taking place for the sake of selection - the ID card would indicate this - or whether they have concluded that they will not pay you.
Possible account unblocking is then the next piece of the puzzle.
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