Custom sounds that have changed from original doesn't apply on all sound types

So I was making a resource pack, then I changed some of the sounds such as "mob/chicken/death" from original to custom. But it turns out that the sounds Doesn't play or apply. But some of the sounds that were changed like I said "mob.chicken.death" is playing if I got these sounds from other resource packs with sounds. Example: got a custom sound (not actually custom, the changed original sound) from other resource pack like mob/zombie/death then i changed into mob.chicken.death then it plays. The example of this issue is when I downloaded a sound or song then I changed into mob/chicken/death then it doesn't play. If this is a bug, Then I will wait but if I did it wrong or you said that I did it wrong, Pls type in the comments on how I can change custom sound and how to make it work. Thank you.