The audio was exported with the video from Premiere the same way I have exported the last 29 videos. It is also the exact same audio track for each video.
What I did in the end was drop the audio track into After Effects. It then played the audio fine and I exported it from there when I was done. Everything exported fine so I moved on to the next video.
On the next video, I did everything in Premiere the exact same way I have been doing for all of the videos and when I loaded the video exported from Premiere into AE, everything worked fine. So, I have no idea what it was that caused the audio from that one single video to no play or export, but everything is working again.
Thank you for your help.