@vladc Thanks for letting us know I can tell "my" users to whitelist your domain, but I 'm afraid that the only way to get rid of this issue is to try get de-blacklisted
The domain is listed in this default pi-hole list: list.2.sysctl.org.domains (http://sysctl.org/cameleon/hosts)
We've emailed the list maintainer asking for an explanation/removal, but we haven't received any response.
That list hasn't been updated since 2018-03-17.