Trigger will not engage On 80% AR-10

[Mikedril]

How do YOU define "fully reset"?

The trigger ONLY needs to release enough for the sear surface on the hammer to clear the sear surface on the trigger.
Any extra movement is a waste and simply creates extra trigger "creep".
You are probably equating the disconnector travel as part of the trigger reset...

We are on the same page. The "disconnector travel" is controled by the trigger. If the bottom of the fire control group "pocket", in the receiver, is not machined to the proper depth, the back of the trigger cannot "reset" or drop down far enough to create the proper "disconnector travel". The OP should check that "pocket" depth. If it is 1.25", and he still has the same issue, he should time the disconnector as you said. If not, he should mill the "pocket" to the poper depth and try again. IMHO.

[Tactical Support]

Don't file out the Pin Holes!!!!! Like KC said it will not help. The disconnector is not releasing try another trigger group then report back.
It may be as simple as tuning the disconnector. I have seen many lpks out of spec lately.