You are using the module system I presume? Under module_scripts.txt, make sure you have the code under the "duel" section, and not the "battle" section.
(this_or_next|eq, ":game_type", multiplayer_game_type_duel),
I'm new to this as well, so maybe it's possible to also have it under the deathmatch section;
(eq, ":game_type", multiplayer_game_type_team_deathmatch
Which makes sense. Also make sure you have the map in the correct order in all the .txt files. Hope I helped.