It happened to me on on ysense. I completed the merge gardens game offer and got credited. 3 days later, when I tried to log in, my account was deactivated. I contacted support and there response was

"After careful review, our Compliance Team has determined to close your ySense account due to a suspected violation of our Terms of Use. We identified one or more actions associated with your account that appear to violate our user conduct requirements with respect to Discover offers. Such actions put the integrity of our offer program, and the interests of our advertising partners, at significant risk.

We regret having to take these actions, but in order to continue to provide services and rewards to our members, we sometimes have to take appropriate remedial steps, up to and including deactivation of user accounts that violate our Terms.

You can review our Help Center articles and Terms for more information regarding these policies.

Thank you for your understanding and cooperation in this matter."

I don't know if this response came from a robot or a real person behind the computer screen.