I am using the release branch of the Popcorn FX UE4 Plugin (v1.3 currently) with Unreal Engine 4.12.5, and I've run into this exact same fatal error when trying to build.
PopcornFXPrivatePCH.h(55): fatal error C1083: Cannot open include file: 'hellheaven/hellheaven_api/include/hh_precompiled_default.h': No such file or directory
I've tried it with several other versions of the Popcorn FX UE4 plugin including the one that worked for the OP, as well as older versions of Unreal Engine, all with the same error.
I have also tried regenerating and then rebuilding/purging Binaries and Intermediate folders, still getting the same error.
I saw this bit on the wiki:
'Sometimes, the archive has not been extracted properly due to path too long, resulting in missing files. Try to extract it closer to root of your drive, then copy paste the directory.'
So I tried that, still no luck.
I am using an up to date Visual Studio 2015.
Surely other people have run into this by now, as I've tried it on 3 computers with the exact same result. I would really appreciate any help getting this up and running.
EDIT: Apparently downloading the file from the clone or download button does not include the SDK files needed to compile, so you have to use link to the Latest Release in the instructions. I'm obviously not the most GitHub saavy person, but it would be nice to have some clarification on that.
Anyhow, up and running now :)