I thought I would post my findings here, in hopes to save any other possible users/ new users my grief!
After thorough testing at my Nikon reseller, it seems the Atomos product line is not compatible with Nikon DX series cameras, at 24p. 30 seems just fine, but no 24p external recording with Atomos. We tested the D3300, D5200, D5300, D5500, D7100, and D7200. The Atomos for some reason won't lock with the cameras. I hope Nikon takes a look at this, as that means no 24p recording on half of their cameras..The full frame Nikons seem OK though.