I might've said this before but other gambling sites do the same thing, they'll usually mention parts of their rules but not show the proof of how they found the link between different accounts.
If you used a vpn maybe that could've caused the issue since they also locked mine (this was before they changed the site) but they were kind enough to let me go after I gave an explanation.
They're probably desperate to get new players because you wouldn't be given a second chance if the same scenario happens on other sites.
I might as well accept their offer to unblock my account by depositing (which is tbh beyond ridiculous to think about), but the fact that they took the balance in my account without any explanation is just non-sense.
Talking about VPN, I didn't use any VPN whatsoever, but I opened my account once in a computer shop where a network of PCs are connected to one internet modem (which I think could be the reason why they thought that my account was a duplicate of another account).
Its even less likely to happen because you said it as shop, if not big one then its almost near to zero chances that someone used the same PC to create an account on Nitrogen.Anyway you are allowed to create a scam accusation against them since they are not revealing any information about multi-accounting but just simply saying that you committed it. So go to scam accusation section and post all these screenshots and wait for the nitrogen sports representative to take care of this case.