Yes. The questions I asked in reply 7.
You're right, I totally did miss that, lol.
You might also do an online virus scan on your computer.
Fresh Windows 10 install. First thing installed is BitDefender, a real capable AV that has very aggressive heuristics and updates its defs many times every day (though personally, I think Kasperky was better - fuggin politics). Second thing is Windows Firewall Control to block all incoming and outgoing traffic by default, and have WFC notify me of all attempted connections, which I selectively create informed rules for only as needed. The third thing I install is Sandboxie, to keep all of my web browsing completely sandboxed from my system (though I made an extra-special exception just for WinCustomize and ran both Floorp and Edge un-sandboxed just to test, then I immediately restored a shadow copy of my system from before doing that because I'm OCD about security, lol).
I keep my systems locked up tight and know what I'm running, from who, and why. Haven't had an actual virus in... literally ever, and been working professionally on PCs over a decade.
I haven't installed much on this system yet either, since I installed Windows two weeks ago. Mostly just Stardock apps.
Just tried it with my iPhone too, same result... that same "access denied" page. So I'm totally sure it's not a virus on my PC.
What are the file names of wallpapers you're trying to upload?
It's all stuff like MistRealm001.jpg as that's how I typically name files. I avoid spaces and special characters, at most I might have a dash or underscore. Really not relevant though... at least not yet. Because I can't get nearly that far. I'm not clicking "upload" after selecting a file, because I can't get to any upload page at all. I'm clicking "upload" on the home page, and being sent directly to an "access denied" page. So my files/file names are not even in the picture yet.