Just got a notice that my Rakuten account was shut down after inquiring why I couldn't access it anymore. I only used it occasionally and didn't do any referrals. This was their explanation:

"We have found a number of accounts in violation of our program terms related to yours. Due to the abuse of our program, our risk department has ended membership for all related accounts."

Totally shocked that they shut me down. It seems like my account may have been hacked and/or my email was used to open other accounts or something. Rakuten was the only cashback site that I used. Like the OP, I wonder if there's anything I can do?