Unjustified confiscation of winnings

Hello. I am writing to dispute the unfair confiscation of my winnings at Bluvegas Casino.
I deposited and claimed the standard 2nd deposit welcome bonus, wagered it fully, and won €2,290. However, the casino confiscated most of it, leaving only €175. They claim I used a "special email bonus" with a 5x maximum cashout limit.
This is simply not true because I took the standard welcome bonus directly on the site, and it doesn't have any 5x limits. To make things worse, the casino website doesn't show any bonus history, so I can't even look at my own account data to prove what I clicked.
When I went to live chat, the support agent actually confirmed to me at first that it was a regular welcome bonus.
I asked them to show me this email or tell me when it was sent, but they couldn't find anything and provided zero proof. It looks like they just don't want to pay me and are using the lack of a visible bonus history on the site to change the rules after I already won.
I just want a fair review of my case. I am asking the casino to show the actual technical logs of my deposit to independent mediators to prove which bonus ID was activated, because I know I used the standard welcome package. Please help me get my €2,290 back.