I did not change anything in the API Explorer, just used the default (prefilled) data.
The «API Integration Guide» does not mention any limitations on the XID
param:
alpha.pwstaging.com.au/docs/api-integration-guide#request-message-
For comparison, here is the XID
parameter specification of another Australian payment service provider (SecurePay): [SecurePay] What is «3D_XID» in a 3D Secure authentication scenario?