Ran into an issue today where audio was working normally in Final Cut Pro X 10.3.2, but the exported video had no sound. The video and sound was originally recorded using a Canon G7X Mark II. The fix was to delete Final Cut Pro X preferences, as detailed by Apple in their discussion forum.
My first video was a good bit of work, taking roughly eight hours to write, shoot, produce, and publish a ten minute video covering some tech industry news. That's not scalable, but it was a learning experience. Here was my process.