I am having a similar problem to the one discussed in this question posed back in August (The file upload questions are not working for audio files in my canvas ). I have created a File Upload Question in a quiz to allow students to upload PDFs. When I am in Preview Mode and attempt to upload a file, I get the little "processing" icon for a second, then nothing. I've read that Flash is a requirement for this function and I've verified that Flash (Shockwave Flash 27.0 r0) is working in this browser. I AM using Firefox ESR 52.4.1 (32-bit), which is not supposed to work with Canvas, but I've had no issues until now. I also tried it with Chrome, but had the same issue.
So any further advice? I've submitted a ticket to our local Canvas expert, but he's on vacation and I need to get this working.
Thanks in advance.