Error promoting customer to Sage 300

Sage CRM 2019 R1 and Sage 300 2019 PU2

We add a new customer in Sage CRM and then click "Promote to Sage 300"

The Sage 300 AR Customer webscreen opens and we can enter a Group Code, when we click Save we get an error message:

Please correct the following issues:

  • A problem occurred and the Customer could not be added. Please try again.
  • An unexpected problem has occurred. Please try again or contact your administrator for assistance.

The customer is actually created in Sage 300, but the Sage CRM record is not updated with all the details: group code, tax group, terms code.

If I click the Customer link it actually pulls up the Sage 300 AR Customer screen with the correct customer.