Update: Looking around I found the issue for me, when uploading a file to CurseForge you're given an option to make the file a Release, Beta or Alpha version. Each of these options are treated differently, Alpha limits download of the file to CurseForge only, and does not update on Curse.com or the client. Beta does update on Curse.com but do not update on the client unless the user chooses to receive Beta files. Release updates with both Curse.com and is publicly available on the client.
A simple solution to this problem would be to simply have a hint/description for what each option does on the file upload page.
Now I'm updating my pack and uploading it as a release.