Access denied error on API docs

http://docs.mattermost.com/developer/API-Web-Service.md

403 Forbidden

Code: AccessDenied
Message: Access Denied
RequestId: A4DA6551444B7042
HostId: +CnchrHymTc1eImYTmxNaSJqsKF5Vr5aw3kKOTBmiWsr974bl8E9HFhLhAQKiRHo
An Error Occurred While Attempting to Retrieve a Custom Error Document

Code: AccessDenied
Message: Access Denied