The v1 deposit API has long been deprecated, and it is now shut down.
The v1 deposit API was originally created to support early versions of Open Journal Systems (OJS). When OJS 3.1.2 came out, a newer more reliable v2 deposit API was created, and the v1 endpoint was deprecated and went unsupported.
OJS users on version 3.1.2 or higher can continue making Crossred deposits using the v2 deposit API. Users of older OJS versions can continue to export your XML and upload it to Crossref systems, or you could and should upgrade your OJS instance to a supported version that makes use of the v2 deposit API (OJS 3.1.2 or higher).