No matter what I do, almost as soon as it finishes downloading it gets automatically removed, and it doesn't even show up in my downloads or anything. I've tried everything I can think of and nothing works, including turning off my anitvirus and going through to change computer settings. I've downloaded the things that it says it needs on the troubleshooting page, but it still won't work. Am I doing something wrong?
What OS do you have? & what browser? Some systems or browsers are set to consider zip files suspicious, so they might automatically have that filetype blocked.
On Chrome, at least how mine's set up, if you look at the bottom of the window it shows your latest downloads. Does it say anything like "File blocked"? Or if those don't show up (or you have already closed that bottom strip), click the 3-dot menu button on the upper right & select Downloads. Is the file in there with any note of being blocked? On either of those, you might be able to right-click (or click the arrow next to? I forget which) it & tell it Unblock.
But if you're unable to do all this, then here's a guide that might have your solution (there are several sections for a few different versions of the problem).
https://www.softwaretesttips.com/stop-chrome-from-blocking-downloads/
If you DON'T have Chrome, then you can try using a search engine with the name of your browser, plus terms like "blocked download" or "how to unblock downloads" or "zip disappears" or something
If you're downloading to a Google Drive, sometimes that has had really weird bugs concerning zip files.
& you mentioned making sure it wasn't antivirus software, but did that include Windows Defender (if you're on Windows)? If you haven't yet, turn off Active Protection for that (at least temporarily) & try again.
I hope you can figure something out.
(I might not remember to check back here to see if you ask additional questions, but I just figured I'd info-dump what I had time to find, just in case it's a starting point toward a solution. Good luck!)