This error happens when ContractorTools attempts to update a customer, job, or transaction in ContractorTools while you have the same customer, job or transaction open for edit in QuickBooks.

The error message will display the name of the customer, job or transaction in the first line of the error message.

To fix this error, please close the customer, job or transaction open for edit in QuickBooks, or simply log out of QuickBooks, and then sync again.