I setup a reseller account with McHost and received my personal nameservers. I went to one of my personal domains to change the nameservers and the NS2 didn't work. I emailed them and they responded with the following message.
It appears that your second nameserver was not fully registered. Please
try registering it again.
The domain is functioning on my McHost account but only with one NS. I am new to this whole process and need some suggestion with what to do next.
Thanks
Trent

When McHost gave you your 2 ips for your nameservers, you need to go to the registrar where the domain was registered from (IE Registerfly, GoDaddy, Stargate, etc..) and register your nameservers there with the IP's the MCHost assigned to you. It can take anywhere from 24-72 hours for your nameservers to show up in the registry.

You should try posting this question to the MCHost reseller forums. There are a lot of really helpful people there that will be more than willing to give you a hand!