Minecraft version: 1.16.3/1.16.4
Forge version: 1.16.3 - 34.1.42 / 1.16.4 -35.1.28
Wyrmroost version: 1.2.10

I tested this on 1.16.3 and 1.16.4. Wild one can still summon lightning on player. Tamed Butterfly Leviathan can't summon lightning when ordered to. I've checked the keybinding and tested only with wyrmoost mod. It will play the animation, roar and the light pattern dims but nothing happen.

Tested on various hostile mobs, while in water or during rain on land. Only attempted it once the light pattern return. Nothing shows up on log.

I remember it working a while back. I tried version wyrmroost version: 1.2.7 and it worked again.

My bad i didn't see it was an issue with tamed ones

The leviathan summons lightning only when targeted at an entity, otherwise it does nothing. Try this.

Late response but I did try to target hostile entity. The animation won't play unless I target a hostile entity, when it does no lightning is summoned.

I have same problem in 1.16.4，when I press the skill button and catch the enemy，she just does an actionwithout thunder.