Hmm, you say "dungeon keeper gold" does that mean you don't have keeperfx? It's not clear from your post.
Either way, portals won't generate any creatures without a script. (Map settings -> 'Edit script', or use the script generator)
But I believe a common issue is how the CREATURE_AVAILABLE function's arguments are different in keeperfx. Read the documentation here: https://github.com/dkfans/keeperfx/wiki/Level-Script-commands#creature_available
Be careful copy pasting from old map scripts, since if they don't have LEVEL_VERSION(1) at the top then stuff functions differently.
For now, keep it simple and see if the script generator works with default settings.