I was having such a hard time uploading some files from my phone or tablet. I would get errors when upload sound files like .avi or .wav; when I was trying to add voice notes from my phone to a post or even uploading pictures taken from my phone. It was not a size issue .
Turns out I had to change a couple lines of code in my themes function file :
// code for add .wav to uploads
// here we go
$mime_types[‘wav’] = ‘audio/x-wav’; //Adding wav extension
you can just paste this anywhere in functions.php
-you have to change mimetypes for different files, I googled a large list to get the right value for the above code.
Overall this was super frustrating but an easy fix once I sat down to do it.