This issue seems to be occurring due to the reconciliation flag in the database appearing to show as reconciled, whereas in the front end the statement is not reconciled and or is in progress.
In the first instance check to see if the transaction is showing as reconciled within Enquiries screen. It might of manually been reconciled after the statement has been created. If it is showing as reconciled, un-reconcile within enquiries and try the reconciliation in cash book again
If this still does not work then our support team will need to investigate, run scripts or liaise with the hosting or development teams. Any Issues with contacting us, please see the following Get support in Access Financials.
Error - 'There has been an error when attempting to update the reconciliation' when trying to update reconciliation
Updated over a month ago