Hey Lou:
How did you set up your pre-set failsafe bind?
Do you have a switch activated failsafe setup in the DX7? If not, you need to do that first. On my DX8, I have that failsafe switched on the GEAR switch. Normal flight=0 and failsafe=1
Next, get setup to bind the AR8000 to the DX7 again. Then with the bind ready to go, set your throttle to above 10% - a lot of pilots are now putting it around 40% and switch your failsafe switch=1 (ON). Now complete the bind.
If the bind took, connect to Assistant with NAZA and DX7 powered up and go to the TX CALI page (I think), where the "U" slider is. Turn off the DX7 and the U slider should move to a failsafe position between one of the flight modes.
Hope this helps since I'm working off memory and with a DX8 and AR8000.
Ron