This version is very old and no longer supported. You need to upgrade (ideally to an 8.x version) as a matter of some urgency.
This is not AWS S3, it's some other allegedly-S3-compatible thing that turns out not to be properly compatible because ...
... this is not how AWS S3 responds to this request. For further information, please see these docs, particularly:
You will need to work with the supplier of your storage system to address any incompatibilities you encounter. Please do not report Elasticsearch issues involving storage systems which claim to be S3-compatible unless you can demonstrate that the same issue exists when using a genuine AWS S3 repository.