Thank you so much, that helped a lot!
Pfff and as I hoped/suspected, the problem was really simple, which was great - but also really embarrassing, haha.
The breakpoint troubleshooting showed the ability didn’t have a valid target. Apparently in my testing around with puppet classes and changing meshs, at some point I replaced the enemy puppet without realising it and never designated the replacement as an enemy. No wonder the attack action didn’t run, it had no enemy to target. Now I feel like facepalming. Leaving this up anyway, maybe someone in the future stumbles across the same dumb mistake and finds this here, haha.
Welp, at least I learned a lot about troubleshooting. Thank you so much again! Your toolkit is a big reason I’m even learning UE in the first place, because this is 100% the sort of game I adore and would like to make for my project and even from outside, the toolkit already made such a useful and comprehensive impression.