Why am I not getting combat EXP?

There can be a few reasons you don't get loot and exp when kiling mobs, but the easiest way to remember is unfair combat is punished! If you think you found a way to grind mobs that's super efficient, with little risk, it's probably hiddenly nerfed.

• Passive mobs don't give exp/loot.
• Killing mobs with enviromental damage doesn't give exp/loot. You need to do most of the damage YOURSELF, meaning those with those damage number particles that appear when you attack mobs.
• Mobs that are too high or too low level from you won't give exp/loot.
• If you're low on Azuna's Favor, you get decreased exp and much worse loot.

If Balance of Exile is installed:

• Mob farms are punished with reduced exp/loot by reducing exp/loot if you kill too many mobs in a chunk
• Spawners disable themselves for a while after spawning a few mobs.

Notes:

• Fire aspect counts as enviromental damage, so yes if you let a mob burn till death you won't get loot, shocking I know.
• Pets don't count, sorry about your wolf armies!
• Some mods could have classified their hostile mobs as peaceful, so it's possible a hostile mob from another mod could not drop loot.

Easy way to make sure you're grinding efficiently is to:

• Fight mobs near your level
• Avoid using mob grinders
• Explore structures and open chests with loot, you gain Azuna Favor this way
• Fight mobs with your own attacks and spells