In my humble opinion the project and/or your preferences may be corrupted. I had the same problem with Avid.
Last week I could’t hear audio on an imported project. When I cleaned my preferences, everything came back to life.
Clear unused media cache
Here’s how:
At the top of the Premiere interface:
Premiere Pro (mac) Edit (windows) Preferences/Media Cache then click on clean unused. If that doesn’t work.
To reset your preferences by: holding down Alt (Windows) or Option (Mac OS) while the application is starting.
ALSO: I’d clear out and rendered effects.
Hope this helps