If you aren't 100% certain you actually did all of those things then try all of them again. Something on your computer, or something related to your internet in general, is preventing the file from downloading.
Also I'm assuming you are downloading from m2.ppy.sh because you tried using the mirror download after the main download link didn't work? If not, try using the main download link, not the mirror.
You can also try running these commands in an elevated comment prompt, but I'm not really confident they'll actually do anything:
- ipconfig /flushdns
- ipconfig /release
- ipconfig /renew