Can't Use Melee On Mastery Rank 3

[colemans2014]

I keep failing the mastery Rank 3 challenge mission because melee won't work. Hence the title. I like to wall jump and cling to the wall before finding the next enemy to attack. Maybe cause it helps. Maybe cause it looks cool. Maybe both. But I've done it 3 times now and each time I did I couldn't melee after. I'm also using the skana in case that matters. It's kinda annoying.