Premiere Pro 2019 Audio Channel Issues
The issue is primarily working with multi-channel audio files that work fine in 2018 but when you convert them to 2019 it appears the audio is missing in all of our projects. The fix is to go back and set the audio channels back to the proper channel e.g. (ch 2 instead of 4 which it seems to keep defaulting)
This also happened when one of the new 2019 projects crashed, all the audio seemingly disappeared until we reassigned the proper audio channel.