For some reason, the service that you provide to these sites is randomly blocking those who have internet services that use VPNs.
This is extremely frustrating and contacting Artstation does nothing since they do not respond at all. I am hoping that you are able to provide some insights into why this happens.
Settings are configured by the site owner, not by Cloudflare. The logs showing which product is blocking a request are visible to the site owner, and not Cloudflare.
If the site configuration is blocking you and the owner won’t tell you why, that is negligence on behalf of the site owner not on behalf of Cloudflare.