If your PowerPoint presentation is not displaying inserted audio on all slides, here are some things to check:

1. Check the audio file – ensure the audio is in a compatible file format (MP3 or WAV) and is not corrupted.
2. Check the slide order – if the audio was inserted in a particular spot in the presentation, double-check that the order of the slides has not been accidentally changed.
3. Check the media settings – make sure the volume on the presentation file is enabled and the audio options are set to play automatically from beginning.
4. Check the timing settings – make sure the slide transition timings have not been set to automatic, as this will override any timings that have been manually set for the audio.