This is most likely to be caused by the data being reconciled for one particular month (e.g. August) when they were transactions in a different month (e.g. April). To correct this you will have to unreconcile the transactions for that period and then reconcile them to the correct date/period.
Another reason for this issue could be a data issue. Sometimes the reconciled transaction will be in the correct period but certain details are missing in the back end of the system.
If the above does not resolve your issue 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 Dimensions.
Amounts showing unreconciled on report but have been reconciled on system
Updated over a month ago