having trouble with hostname resolution

ok, I am using skysilk for my vps, I am trying to get my host name to pass the checks, but each time, it fails, what am I doing wrong?
the default host name was not working, so I changed my vps hostname to my domain name, then went into the admin cp and set it to host.cybertrongaming.ga and this is the error I keep getting

Your Hostname is: host.cybetrongaming.ga and it resolves to IP: (ERROR: You don't have a valid hostname set!)
rDNS/PTR = FAILED, check with your hosting provider! FAILED

Changing a hostname only on a VPS are not enough steps to take, to get the  outcome you want.
You also have to take a look at your DNS records, they are more important.

an vps has ONE hostname, but can serve many DOMAINS