Something else, I've checked the above 3 and they don't apply to me.Your applications user agent is incorrectly configured.You are using an outdated program that makes use of bad practices or old API endpoints.
There are a few different reasons that you can run into this message: It's great, and probably does what you want! 403 Access Denied - Oh no! If you were using a script/program you found to try and download content, it's likely that the script was what resulted in your request being blocked.