If your problems are with the 777 v1.6, then v1.7 is out now! Check-in to Your Profile > Product (777 Captain (777-200) Base Pack [P3D]) > Extended Download Service > Get New Links, and download the latest version of the Captain Sim 777. The ACE for the 777 should work in P3D v2.x/3.x.

I have the 777 Captain installed in P3Dv2.5 and P3Dv3.1, and the ACE works fine for both of them. :)

Note. You need to get the latest versions of the Expansion Models (777-300 and 777 Freighter).