I imported mp4 files from my Go Pro to a timeline. Sound was working great. I added some text and restarted the playback, and now no sound. I did not do ANYTHING except added text in Expert Mode. Running Premiere Elements 15, totally up to date. WTF? This program is pretty glitchy. BTW, I have i7 latest generation, 16 GB of Ram, Realtek High Definition Audio. Sound works on PC, just not in PE. If anyone has seen experienced this issue before, I would greatly appreciate feedback. Right now, I am rendering the video to see if this corrects the problem.
Sorry you find the software glitchy on your exceptional computer. I've never experienced any issues on my ASUS laptop and edit 4K routinely.
Consider sharing a clip on DropBox. Maybe something can be figured out.