Adding narration as an "afterthought"

Okay now I have a whole new issue, my project was just about done, everything was working, than I added some narration that I imported from itune using a m4a file and everything was fine. Than just now I used an external microphone went in an changed my ASIO setting to recognize the microphone and than all of a sudden that is all that is working on my timeline. All of my music is muted and will not play back. I than removed all of the narration files that I entered, checked my ASIO setting and it shows my speakers. I saved the program and did a shut down of my computer and reopened the Premier Elements all of my music is on the timeline but won't play. It is like I all of a sudden have a bug or corrupt files that are causing the problem. I was ready to burn my disc and now this after many hours of time on the project is appears ruined.

https://forums.adobe.com/people/AZ+Aurora  wrote I do not want to add the narration and then have it affect the rest of my timeline.

I'm not sure what you are asking.  Can you rephrase the question?

Also my audio files are mp3 and m4a, my narration are wma files, will that be a problem?

Maybe, maybe not.  I would convert the audio files to wav.