Help, enemies don't appear when i test a map.

Hi, i'm new in Doom Editing World and i am from Argentina, sorry for my bad english, i have a problem with the Doom Builder, i can place 1, 2 or 50 monsters but they don't appear when testing a map (The monsters are not custom, they have all flags (Easy, Medium, Hard, Deaf and Multiplayer) and there is not a parameter that makes that monsters don't appear) I use a program called bGZDoom and i load the textures of doom.wad and DOOM2.wad...

Please, can somebody help me?

This isn't exactly the place to get help since not many people even know how to get here. But yeah you've probably set it to no monsters via the testing difficulty not the parameters. There's 2 sections under the test drop-down menu with the difficulties. The top section has a live cacodemon and the bottom section has a dead one. The dead one indicates no monsters.

flagging a monster as multiplayer means it will only appear in multiplayer, so if you're testing in single player they won't be present. so just remove that flag and it should be fine.