The validation for the "iss" field in the OBRegistrationRequest1 object (in DCR v3.1) is as follows:
The guidance for this is as follows:
For SSAs issued by the OB Directory, this must be the software_id
But the software_id issued in the OB directory is 22 characters in length so is not valid according to the spec. I've noticed the 3.2 registration spec does allow for this length, but most banks don't support this registration version yet. We can register with banks that don't validate this or banks that implement the 3.2 spec, but by the looks of our registration attempts, Nationwide validates the length and doesn't implement the 3.2 spec.
Unable to integrate with Nationwide
None possible unless action is taken by Nationwide
Unable to register, and therefore integrate at all with any Nationwide APIs