Step 1: Navigate to Settings.
Step 2: Proceed to Integrations.
Step 3: Select QuickBooks.
Step 4: Click on Map My Customer.
Step 5: Start searching for the customer causing the error.
Step 6: Continue your search here if necessary.
Step 7: Ensure you've found both customers.
Step 8: Confirm that both customers match.
Step 9: Once you've matched both customers, click Save.
And that's it! You've successfully resolved the QuickBooks error.