GA bug causing it not to proc

I was jungle WW with Skirmisher and devourer enchantment. At 40 minutes in, our lucian and I caught their Vel'Koz out. When we killed him, his newly bought GA didn't proc. I ulted and used the smite after my ult. I do have the game recorded from obs if any Mods need the video to actually see it in action.

Match Details in link