Hi,
Copying the file require a bit of collaboration between the vCenter server, the VM/host, and the plug-in. In the first step, we call a vCenter API to initiate the file transfer to guest. As a result, vCenter returns a URL, and then it is a responsibility of the client (in this case, the vCenter plug-in) to make a HTTP PUT request to this URL with the file content to copy in the request body.
This HTTP request must be secured with a X509 certificate for the host. The plug-in has code to do so, but maybe there is some issue with special deployments like your OVH vCenter.(I assume your other vCenters where this work are not OVH, is that correct?).