Alright, long story short, here was my setup:
Asus RT-N66U as my main wireless Access Point. Asus EA-N66 acting in Repeater Mode. And NO Airplay was working. No matter what I connected my devices to - the main Access Point, or the Repeater, Airplay would not work. Airplay devices would not show up. Just basically at a loss.
After trying a bunch of things - I e-mailed ASUS - and as it seems with most routers - the issue was the firmware.
I upgraded the EA-N66 Repeater's firmware to the latest at this link:
And all was fine! Everything was working again!
Hope this helps some peeps.