Well that sucks. Did they give a reason for banning them?
Here's the email they got:
Prolific Support Team
Hi, We carry out various types of automated checks on accounts to improve data quality. These include assessing responses to surveys, reports from researchers, information you have provided us with, as well as other factors such as IP and device information. As a result of these automated checks your account no longer receives surveys. I have looked into this for you and can confirm the validity of the checks. We are unable to disclose further information about what these checks are, as they are critical in ensuring high data quality. We apologise for this inconvenience.
You can still cash out any remaining funds.
Best, Prolific Support Team