Accidentally current posting period got closed. Need to restore the old period.
Please provide the details steps or any SAP notes which can reverse the posting period.
Use T-code MMPI
Check with -OB52 ( Control the Opening and closing the period for posting )
Also Follow the instructions in Note 487381 before initialization
see note 487381 - RMMMINIT: Protection against unintentionial execution; basically you have to: