Export a video but one audio line was missing.

Hello,

I've just finished working on a documentary and exported it but turns out there's an audio lines missing in some part. However, all the missing audios can be heard when listening with head phone or play it on PC with players like VLC, windows media player (I've try with players I have) and also on Youtube, Drive etc. The sound is silenced when I play it on my phone with no headphones, or play it with any speakers. I can hear other parts like music and ambience sound except for the voiceover. Also, all the missing audio parts are from the video which was shot with the same camera. Please help, I've been digging every forums and websites for this kind of error but found none. I'm supposed to deliver the files tomorrow too.

Best.