There is no need for forum members to login to to your account. I would advise you to never allow anybody to access your account regardless of the reason.
Keeping that aside, you have stated you cannot think of any reason why Shuffle would treat you in this way. Their lack of communication has not helped you understand why they came to that conclusion. I think it is important they post here to explain what happened according to them. If they continue to to ignore you then you might have to create a flag.
I cannot think of any reason. When I was losing they were treating me like a king, offering extra lossback and what not. I started to get lucky with some casino and later sports win, and suddenly withdrawals were stopped without any communication at all.
I am still happy to offer login to my account and you can check I made no shady bets. Some forum members suggested against it but I am happy to still do it, if required and forum members suggest going that route.