OOC:
So, while you did get an advantageous position over him by succeeding the check, Nez, you didn't actually accumulate any advantage, which is necessary to activate Knockdown. He's essentially in some sort of lock, but not physically on the ground.
Likewise, you didn't generate any advantage, so you weren't able to activate the Disoriented quality. (Most weapon effects aren't automatic and instead need advantage to activate.)
Also, can you add in the difficulty to your roll above? RRP+KK. And boosts/setbacks don't cancel, so go ahead and add in your other boost, as well.
[ +- ] Takedown weapon
If a takedown attack is successful, it automatically activates the Ensnare 1 weapon quality without spending any Advantage. Further, if the attacker does not have the Advantage necessary to activate the Knockdown weapon quality, they may delay dealing damage by one round, and bank any excess Advantage for their next attempt. On their next turn, assuming the target hasn’t successfully escaped the grapple, the attacker may make another takedown attempt. After tabulating the check results, if the attack is a success, they may choose to add the banked Advantage to activate the Knockdown weapon quality, or bank more Advantage. If the Knockdown weapon quality is activated, then damage is calculated from the results of the most recent check.