I started looking at the scenery.cfg files for both FSX and for P3D. I guess that during the install process of KATL 2016 - P3D, changes to the scenery.cfg file did not occur. Not sure why.
I went ahead and added the following to the P3D scenery.cfg file:
[Area.128] Title=Imagine Simulation - KATL Atlanta 2016 P3D Local=Imagine Simulation\KATL Atlanta 2016 P3D Active=TRUE Required=FALSE Layer=128
Area and Layer number "128" was the next in line so after I made the changes, EFB loads up and works just fine.
Thanks everyone.