Packing Failing on 4.12

I recently moved the build of my game from 4.10 to 4.12 and when I tried to package it up (via the Windows-64 settings), the cook fails… every time. I’ve reinstalled Visual Studios and (i think) i set C++ as my default language and it still fails. As an experiment, I opened a new third person project and cooked it right off the start and it worked so it’s probably something with this game specifically. Please help, thank you!