Players Are Invincible On My Server

Hi, I have been running a Bukkit server for a few months but recently I changed the map, added plugins, removed plugins, created a mob arena, created a mining arena, etc. Now we are in the testing mode for all of these new things. I had a few testers come on and try out different permission ranks and see what commands need fixing (I use YAPP as my permissions plugin); after testing, everything works great, except one thing, everyone except ops are invincible. I am not sure why this is, the game mode on individual players and on the entire server is correct, no one has god mode, and no one has other invincibility commands. Monsters still target players but when the players are hit, they do not turn red, they do not lose health, and they are not knocked back. We tried to test this with other things besides monsters such as drowning, TNT, and the void. The void is the only thing that killed anyone. Does anyone know why this is? I figured it might be a plugin I recently installed, but I don't understand why that would be. Keep in mind that all ops can die just like in a normal game. Any help is appreciated!

 

Smart_Guy123
Well, it probably isn't a plugin because most plugins that allow godmode cancel player damage, like when the player falls into the void and get damaged, it is up posed to be canceled.

 

I'm still a bit new to bukkit and such, but I am an IT guy and this kind of thing happening on other types of systems is usually a permissions problem.

Can you post your permissions configs?

EDIT: And a complete list of plugins.