Ok, I totally rebuilt my project from scratch and it was a multi-hour hassle. Hopefully, this will save some of you some time.
The codesign error that I was getting was for some bad audio data! I actually had a couple types of issues:
(1) One of the graphics in a directory was a symbolic link. This won’t work with Apple’s code signing process.
(2) We have only about 6 WAV files as everything is MP3. But those WAVs had something wrong with them that made codesign fail, so I resaved those files back out after making sure the bit rate was 44khz and had no funny headers or anything in them. Then, just one WAV file ended up being a pain (codesign kept failing) so I made it a 22khz file and that worked.
When I rebuilt the project from the CoronaEnterprise ProjectTemplate in Xcode 8, everything went smoothly normally, except for plugins. For some reason I was getting an error about libplayer.a and Xcode said it couldn’t find the CoronaEnterprise/Corona/ios/lib directory, but of course it’s right there.
The fix for this was to copy all the plugins I’m using into that directory, then drag those .a files into the “Link Binary With Libraries” section of the Target section.
Now the game runs in the iOS Xcode Simulators as well as builds to iOS devices and can be copied to the devices. Now I can TestFlight the game again.