Is there an error message displayed ?
You probably don't have the corresponding maps. These maps are provided with the official IDsoftware
Quake II 3.20 full patch.
I've just realized that the link provided in the COOP or DIE guide no more works.
You can get this patch on quakedev.com :
http://www.quakedev.com/files/on fileplanet :
http://www.fileplanet.com/6582/download ... 6-full.exeor on IDsoftware :
ftp://ftp.idsoftware.com/idstuff/quake2 ... 6-full.exeIn fact these 3 missions use some deathmatch maps with added monsters and items.