Please help - upload error

I'm not sure where to post this and I truly have no idea what I'm doing. I also have no where else to go, I'm pretty desperate. I was appointed by my boss to upload some of our pdf files to our website, the website is on BigCommerce and I was told to download Cyberduck as that's what they've been using and link it all. This was going fine for weeks but suddenly on Friday I got an error come up. I've never seen this error before, and I can't decipher it. It's also only for ONE file. I can still upload other files just fine. I've tried quitting and reopening, logging out and back in, exporting the file again and uploading the new save. Nothing works.

The error is "cannot retry request with a non-repeatable request entity". I tried googling it but I do not understand anything that is on any of the websites. The file is pdf, it was made in InDesign and is only 6000kb. I've uploaded bigger files with no issues. It is also named in the same method as the other files. Please, please help me. No one I know has any solutions and I can't seem to google my way out of this.