Sometimes you might see the error message that “Fiscal period for is not open”.
To verify the status of the Fiscal period and change it, if needed, you can go to General ledger > Setup > Ledger > Ledger calendar button.
Find appropriate period and check the Period status. From this form, you are able to change the status to any of three: On hold, Open, Closed.
Note: Do not forget to change the access level for the On hold/Closed period if needed.
The tricky is that you cannot change the status from Fiscal calendars form itself (General ledger > Setup > Fiscal calendars), because Period status column is invisible.