FOLLOW UP........
I managed to fine the right person at Apple and he spent several hours trying to help.
We did everything to my iMac that you could think of, including partitioning the hard drive HD2, doing a "clean" install of El Captian on HD2 then loading ONLY ReplicatorG. This eliminated any 3rd party items/programs that might be causing the problem. ReplicatorG still will not "find" the FlashForge motherboard.
This all points to a driver that is not up to date from FlashForge. On the FlashForge web site it looks like all the driver information is about 100 years old.
I'm still hunting for a answer....
Don