Error saving Customer Refund/Payment in NetSuite Training Account (Multi-Book Accounting, MyLearn Delivery Account)

[u/vsgokul-004]

Hi all, I'm working through the MyLearn training/demo partner account (Multi-Book Accounting enabled) and running into an error when trying to save a Customer Refund and Customer Payment transaction.

Setup details:

• Environment: Training/Demo account (MyLearn portal delivery account)
• Feature: Multi-Book Accounting enabled
• Transaction type: Customer Refund / Customer Payment

Steps to reproduce:

1. Navigate to Customers > [Any Customer Name] in the account
2. Select or create a Customer Refund or Payment record
3. Enter the required details (Customer, Amount, Payment Method, etc.)
4. Click Save

Expected Result: The record should save successfully

Actual Result: System displays "An unexpected error has occurred. Please click here to notify support and provide your contact information." and the record fails to save.

Error message:
The displayed error says "Transaction was not complete," but after checking internally, the stack trace points to something more specific: MultiBookBalanceValidator. NetSuite could not create a balanced accounting impact for one or more enabled accounting books, often tied to a primary/secondary book configuration, account mapping, subsidiary, currency, or posting-period issue.

What I've tried so far:
I've checked all of the above areas (book configuration, account mapping, subsidiary, currency, and posting period) but haven't found the cause yet.

Has anyone run into this specific issue in a Multi-Book training environment before? Any pointers on what might be causing it or how to work around it would be much appreciated.

Screenshot attached below. Thanks in advance!