PaygateDeveloper documentation
404http.unknown_hosthttp

This host does not serve this surface

Returned by the implementation; no specification rule declares it yet.

The request arrived at a hostname that is not mapped to the surface you are calling — a partner call to the console host, for instance.

Why the API refuses

this host does not serve this surface

What to do

Use the base URL for the partner surface from your environment's configuration rather than assembling a host from parts.