Can't pick up knife automaticlly

[JUst7ins]

I already set:

mp_drop_knife_enable 1
mp_drop_grenade_enable 1
mp_death_drop_gun 1

and when I droped the knife , I cant pick it back up anymore, I have to 'kill' or revive again to have my knife back
I'm using the weapon skin changer plugins, but the gun seems does'nt have this issue.
Is this a bug or Its just how it works?
Plz help
(forgive my poor English

[JUst7ins]

Just solved it by adding

ent_fire weapon_knife addoutput "classname weapon_knifegg"

in your console