Hmmmm what does it say when you try to recruit agents? Agent limit reached?
This would only happen if you got VanillaMod installed (it limits the amount of agents (spies and diplomats) you can hire to 1 per basic building and higher for advanced), but not if you only got KOTRfix.
Merchants and Priests are limited by default by the game, although that can be switched off.
Bookmarks