Can't Resolve Hostname on a Friends Server with a custom modpack.

[Grubbulator]

My friend is running a custom modpack on a private server. I have the correct modpack and I'm running the latest version of the launcher. Made sure to unblock both minecraft and the launcher, but nothing I do seems to alleviate the issue. Looked around on the forums for awhile but couldn't find anything. Any help would be appreciated, thanks!