POE 2: META Gem is not triggering for

It seems the build for Cast on Minions Death or any META gem for spell cast, will not trigger of the Monsters are spawn in map after initiate the Breach/Delirium/Treasures/Rituals, occasionally, the Trials too!

Please look into it.
For normal Tier maps monster and the campaign runs, it seems working fine.

I have experienced exactly the same problem. Interestingly, the newly spawned mobs are ignited by the Raging Spirits/Infernal Legion, however, the Fireflower/Necromantic Amulet combo is apparently not set of by this. This leads to the Raging Spirits just despawning as more are created, not "dying" as they are supposed to and fueling the Meta Gem.

There is indeed a bug with the infernal legion and fireflower amulet interaction that will not work on any mob that is spawned after the map is loaded. It's near impossible to figure out if its the ignite failing to apply from infernal legion or the fireflower amulet interaction isn't applying to the ignite on those specific mobs. Ive spent hours trying to figure it out but with the low lvl SRS attacking and the infernal legion ignite so weak I cant tell which is doing the damage to the target. I have tried to time it just right where an srs dies right as it ignites an enemy but I haven't had any luck.