Players can't trade with Villagers.

Hello, I'm currently having an issue where none of my players, including staff members can right click to trade with regular villagers. I've tried going through my config files to see if there was something blocking it but I wasn't able to find anything. Would anyone happen to have any idea? I have these plugins installed:

-BiomeEdit
-BottledExp
-Builder
-Citizens
-CoreProtect
-Essentials (Pre, Antibuild, Chat, protect, Spawn)
-Herobrine AI
-Idisguise
-BukkitCompact
-PermissionsEX
-Minigames
-Openinv
-Playerheads
-Sentry
-Vault
-Shopkeeper
-WorldGuard
-WorldEdit

Thanks in advance.