Skill doesn't work when I press Shift + lmb, only works using hotkey? Is this a known bug? Can anyone provide an answer please.

Do you have the skill locked in the skill window?

No, it's unlocked with the rest of the skills. 

And youre in Awa stance? Might want to do a reset of your skills, or apply a different skill preset. Sometimes skills act like theyre locked even if they are not.

Figured it out. My action button for lmb for some reason got disabled and wasn't allowing my left click at all. It's all fixed now.