I am also experiencing this issue, and I am also unable to download anything from the replay center. I noticed that the folder "/fml" does not exist.
I found a fix!! Use the mirror, because the main link actually is incorrect and is the same as the "Replay Mod v1.12-2.0.0-b7", instead of "Replay Mod v1.12-2.0.0". Use THAT with forge, and it should work perfectly.