First time heard about the Gokumarket exchange. Seems they aren't allowing users from my country, so I can't access the site from here. Did quick research about that exchange and didn't found many suspicious issues. As per CMC, they have a good trading volume as well. There are many positive reviews on Google, who knows if all are fake. But I assume there should be real feedback besides fakes. What exactly they are asking you and what is the error? Are they demanding KYC? If so, then most likely you have to comply with their Terms & Conditions and wait for their response.