There is a possibility that there is something missing. It may be the map itself, not the files. Is this map a single or connected to other portals? I can be wrong here, but people have come across having issues with missing portals due to the connection of portals within a map. If that's the case, the owner must give you the download for the main map. And if it's not the case, then you have done something wrong. Ask one of your friends if they have this map and how they allowed it to work in the game. You are always given files that are put into the exports folder, these are:
.fhm
.fho
.fhs
.fhw
If you have done that then I guess the files are corrupted and no longer work.