title says it, i press the singleplayer button and nothing happens

You haven't edited the main.menu file included with UGX MOD. At the top it asks you to enter your maps .ff name and your maps display name, its shown in the tutorials by UGX Treminaor.

http://ugx-mods.com/wiki/index.php?title=UGX_Mod_Standalone_Installation#Menu_Settings

If you have more than 1 map in progress use the console to launch until your ready for final export than edit raw/ui/ main.menu as a text file before your final compile/ release.