Cannot access ACCESS Front End Database from VPN

I’m helping my roommate out for some extra money. I built an Access database for her company. There are only four users. I haven’t played with Access in the “database design mode” in about two years. One of her co-workers attempted to open the FE of the database from a VPN and could not connect. Is there anyway to fix this. The FE is on her computer, but the back end is on the server. I’m getting more detailed information about this tomorrow. May I remind you that I’m not up to par on the topic and the people that I am dealing with are idiots when it comes to this stuff.