MP4 not registering audio when dragged in

Hi. I have an 8-hour mp4 file, downloaded from DropBox, that plays fine from my desktop and external hard drive. When I drag in to Resolve 16, the video plays, but the audio does not, and fails to register on the audio meters. No WAV forms visible on the audio tracks, either. I've been working with files from the same folder for days, but this file is the only one presenting this issue. This is for a project due tomorrow, and I'm a beginner/intermediate-lite Resolve user -- ANY help is apprecated. Thank you.

Well, never mind. Still not sure what was causing it, but a friend and I solved it by putting it through handbrake and exporting as a new MP4, which Resolve then accepted. Still happy to hear any theories about why this happened, but the issue has been laid to rest. Thanks.

[Dwaine Maggart]

Without knowing your system details, it's hard to speculate.

But you could use MediaInfo (it's free) and look at the before and after file and see if the audio format was changed.