For some reason when I try to upload a replay, it says upload failed. I have checked, it is in the correct format. Can someone tell me why this is happening?

could just be a bug (maybe)
try restarting it

Restarting the site or the game?

the site

Nope it still isnt working.

Try seeing if the replay isn't corrupted by opening it in Toribash, then maybe attempt to save it as a new file, go to all files and then .rpl once again.

ok I shall try it
Still doesn't work

This happen the same with me. But i can upload the replay. And when you want dowload you cant.

Maybe is the Forums working somebad. For some error.