HTTP Error

I keep getting one of two things when I try to upload PDFs…

1) If I upload from the media tab, I get taken to a nonexistent page…https://www.leilaviss.com/wp-admin/media-new.php

2) If it’s from the page where I want to insert it, then it simply says “HTTP” error.

My host has increased by PHP file size and there’s nothing else they can do. I’ve tried a several browsers, disabling all plugins, and a new theme.

Please advise.