You have to specify animations types in order to let ItemsAdder play animations based on the entity state.
The ItemsAdder Blockbench extension does that automatically on conversion, but sometimes you might have strange animation names and it could not automatically recognize them.
Right click an animation and make sure the animation type is correct.
You can set some special animations by settings their name instead, as some new features are not avilable in the dropdown menu.
Rename your animations to this.
idle
idle_angry
walk
walk_angry
jump (used by Slime for example)
attack
death
fly
Notes
This extension supports animated scale of bones. Make sure to avoid scaling when it's not needed. Check your keyframes.
Avoid adding too many rotation, details and movements, don't forget this is a blocky pixelated game, use its style.