I've tried using the Vype Cannons with the cannon balls that are bought at the same npc and I can't get the cannon loaded. I've seen the question asked in server chat, but no one answers. Can someone help explain how?

Bugged and you don't need cannons to kill Muraka anymore.

That makes sense. Big problem is quint and muraka hit so hard that I wanted to try the cannons for damage. Guess I'll stick to hitting them a couple times and then avoid them the whole fight...