Harbinger, is it glitched?

Just completed The Breaking on Legendary with score attack (I’ve used the points as a kill feed to know when someone dies since H3) but did not get the Harbinger Achievement unlock. This took me an hour and a half…is there a glitch because I didn’t view cutscenes? I just want some feedback before attempting again.

Update, the achievement Harbinger does NOT work with Score attack on. GLHF