Why does OSU return a "forbidden" error message?

OSU returns a "forbidden" error message because the v4 version of the API signing process is currently supported for the eu-west-2 and us-west-1 Regions only. For other regions, you need to use the S3-compatible gateway provided by the Ceph community, which is compatible with the v2 version.

For more information, see About Tools to Use OSU.