Is it a server you made, or one your are re-hosting? If it is a server you made, does it say it is approved in Portal, or pending?
The server your hosting needs to be approved for them to be able to find and join an experience code. It also depends (or at least used to) on if your crossplay options when hosting match theirs when they are searching. Lastly, if you are in different regions of the world, that might make finding the server harder from a different region.
A probably better method is that the friends who join you while in your squad, can leave your squad once they get into the server onto the same team. Then other friends can join your squad which is now not full. Then, use the voice chat of your choice applicable to your gaming platform. In other words, once you are in a non-matchmake server together, being in a BF6 party doesn't matter any more to the ability to stay in the server together, indefinitely, round after round. Use a voice chat option that will allow you to talk among the bigger group.
The first reply doesn't know what they are talking about. They are clearly uninformed and jaded.
