Another possibility is that if you are using a VPN or a proxy and another user abused a bonus promotion this could make it seem as if you were part of that abuse even if that was not the case.

However even if that was the case your account could still be banned as the majority of the casinos do not allow people to use a VPN as this masks their location and many casinos have some restrictions about the countries from which you are allowed to gamble, and as such they do not see with good eyes something like this.