I know I am probably missing it but can you activate an weapon quality on a failed check?

No it must be a success to work unless you fail so hard then your weapon may break

One thing about this system is that it really encourages creativity. In some instances if you failed a check yet got a net advantage I might see a weapon quality being activated. As with all RPGs, whats in the book is a guideline and should not be a limited list of options.

RAW, a net Success is required to deal weapon damage . Unless a weapon quality specifies a "successful check," however, it looks like all you need to activate a quality is the requisite Advantage. Knockdown, Ensnare, Sunder, Concussive, Guided, and Stun all appear to not require a "Success" to activate. Linked, Blast, and Burn all specifically require a Successful check to activate.

This all seems pretty reasonable to me, given the rules regarding Success and Advantage with other non-combat skills.