Cannot close period when there are source documents remaining to be journalized with an accounting date within the period. Error ???

i am trying to close periods in LedgerCalendar in General Ledger-> Ledger ->  Ledger Calendar 

but it shows me the following message 

Cannot close period  when there are source documents remaining to be journalized with an accounting date within the period

AX Version AX 2012 R2 upgrade from FB

any suggestion how to solve these ???