Adding new bank account with opening balance

I've added a new bank account but forgot to enter the 'opening balance'. 

I've gone to EDIT account and added the opening blance, but MYOB just keeps showing; "

"Failed to update accounts: transactionDate must be after lock date of 2021-06-30".  

Todays date is 8/6/22, which is after my set lock date, so why won't my opening balance amount save?