This error would be caused by the presence of reconciled transactions in the statement. It can be resolved by following these steps;
Check the reconciliation flag which can be found in the Rec column on the statement and ensure that it has a status of C for all reconciled transactions.
If the flag status is R, to set it to C, click Undo Reconciliations icon (blue arrow pointing backwards) on the Auto Bank Reconciliation window.
Note: This will undo all reconciliations in the statements and any required reconciliations would need to be redone.Click the Reconciled tab when a transaction with a reconciliation is highlighted and click the Remove from Reconciled list icon (page with blue line and red cross). This will unreconcile the highlighted transaction.
Repeat step 3 for all reconciled transactions.
Click Save icon.
Close the Auto Bank Reconciliation window and reopen it with the statement reference.
Click Delete Statement icon (white sheet with red cross).