Error 'The Purchase Ledger Period End cannot take place while the Sales or Nominal Ledger Period End is being run!'

This error is due to the system believing the Sales Ledger Period End is still going on and can be fixed by clearing the Multi User flags. Please see this article on how to do this.

*Note* Before clearing the Multi User Flags, please ensure that everyone is logged out of the system and you have taken a backup of your database.

Error - 'Another user processing/allocating/posting/reconciling transaction or editing project/order '

Enable Period 13 for Year End Adjustments on all ledgers

Unable to post transactions after using task manager to close Dimensions during a period end (Nominal Ledger)

Error - 'You cannot continue with the Period End as there are rollback transactions in the current batch (Nominal Ledger)'

What should I do if I accidentally roll forward a ledger to the wrong period?