I am not able to undo previous bank reconciliation although I logged in using accountant account, how I solve that? I am using QBO Essential Global version

Thanks for dropping by here in the Community, @NhanNg.

I can share some clarifications about the reconciliation feature in QuickBooks Online.

The ability to undo several or entire reconciliation is only possible if you're using QuickBooks Online Accountant. Since you're using the Essentials version, you can only unreconcile one transaction at a time.

Here's how:

1. Go to the Accounting menu.
2. Select Chart of Accounts.
3. Find the account and select  Account history.
4. Select the transaction you want to unreconcile.
5. Review the check column. If the transaction is reconciled, you’ll see an “R.” 
6. Select the box and keep clicking it until the box is blank. This removes the transaction from the reconciliation. 
7. Select Save. 

I've also included some articles in case you need more ideas about how to undo reconciled transactions as a user, as well as granting access to your accountant:

• Undo and remove transactions from reconciliations in QuickBooks Online
• Add or remove an accountant

Feel free to hit that Reply button if you have any other questions. Have a great day ahead.