Try bringing down your console in-game, and typing:
map mapname
If it says it cannot be found, try typing:
maps *
to list all the maps for the current mod (assuming you are using Steam).
If you are using WON, try:
maps esf_
to list all maps beginning with "esf_".
If it doesn't load or get listed, double check that it's in your maps folder, and not in maps/maps or something similar.