Problem with File upload

I am using the file upload on my site and from my testing, if I check my site in incognito mode or if any customer do, the file upload does not work. I am getting a lot of customer email about the upload not working and I did all I could think of to make it work (allow all filetype, allow big file size), allow anyone to upload.

I’d really like to get some help on this as this feature of the plugin is needed for my store to function properly. Thanks for your time!

The page I need help with: [log in to see the link]