See the other thread here about Bitdefender and Malwarebytes flagging the game executables as a false positive. Perhaps there's another program doing the same on your machine.
According to this, I don't think it has to do with anything locally:
This error means you don't have permission to download this file from the server.
I'm not sure what's the difference between that and outright throwing a 403 Forbidden error, but I assume it has to do with forbidding mid-download.