For example, if I have:

#Spawning options for minecraft:zombie
[minecraft.zombie]
  #Should the entity be allowed to spawn normally?
  allowNormalSpawning = false
  #Should spawners be able to spawn the entity?
  allowSpawners = true
  #Should spawn eggs be able to spawn the entity?
  allowSpawnEggs = true
  #Should the entity spawn via mob conversion? i.e. villager -> zombie
  allowConversions = true
  #When enabled the entity type will be aggresively removed from worlds. This will bypass all other options.
  removeAggressively = false

and use a spawn egg, I hear the zombie noise, but it never spawns. Not sure what could be happening; I looked at the code and it makes sense to me.

Minecraft version: 1.18.2
Forge version: 40.1.54
Mod version: BadMobs-1.18.2-13.01.jar

Can confirm this as well.

Can also confirm on 1.16.5

yeah this issue happens to me too pls fix it when you can (mine is 1.19.2)

Just spent 2 hours setting up this mod only for it not to work. Also using 1.16.5

PLEASE PLEASE FIX THIS MOD. This is the only issue stopping me from making a high quality mod pack :(

Just spent 2 hours setting up this mod only for it not to work. Also using 1.16.5

PLEASE PLEASE FIX THIS MOD. This is the only issue stopping me from making a high quality mod pack :(

You could try https://www.curseforge.com/minecraft/mc-mods/in-control for disabling normal spawns only. The configuration is a little more complicated, but it works for me.

This issue stems from a bug in Forge. They're trying to fix it in 1.19.4, so hopefully we can finally fix this issue.

Forge was able to fix this issue on 1.19.4 and the mod appears to be working as intended now. Unfortunately older versions will not be receiving this bug fix.