What version of Premiere Elements and on what computer operating system? -12
What sound is not heard - that from numbered Audio Tracks, Narration Track, Soundtrack? - I don't hear anything
How many prior saved closed project files (prel) have you opened and could not heard sound the existed in those files when they were saved closed? - a few
Same particular audio file involved in each case?
Can you open a new project and maintain the sound before and after save close reopen? - yes
Did you create narration using the project's Narration Tool and add it to a Timeline already consisting of Soundtrack and other non narration audio? - yes, but I deleted it and still the same result( no sound)
Let us start here and then decide what next.