An order for the .nu domain registration with OPENSRS fails:
Domain registration failed. Domain registration submitted to OpenSRS but there is a problem. (465) Invalid data The registrant type must be specified Domain status:Prepared<1 time(s) called.>
.NU domain registration requires additional information for an individual or organization, where an individual must submit an ID number and an organization must submit a VAT number and a business registration number. You can refer to the registration requirements in the Domains API Command Reference Guide, under the TLD_DATA section on page 59.
PBA does not support .nu registrations via OpenSRS, there is a feature request #PBA-51786 to implement such functionality.