Addon vehicle help

Hoping I can find out whats going wrong. When installing addon vehicle packs, it does not actually add new vehicles, just replaces existing models. I’m at the office, so I don’t have access at the moment to everything, but I was hoping someone could nudge me in the right direction or give me some idea what to try next. I’ve got my tech guy on this, but I think he’s over-thinking it. If this isn’t enough info, please let me know so I can get the help needed to fix this.

There’s already tutorials about this on the forums, either in #development:tutorials or in #server-development:server-tutorials, if that doesn’t work for you try looking at some resources like these [Release] Captain14's ELS Style Car Packs and see how that’s done.