It's great to have you join this thread, JLM17. I know  the reason why you're unable to see the undo option when viewing a previous reconciliation in QuickBooks Online (QBO).

You're not seeing the Undo button with your previous reconciliation in your account because you have a regular QBO subscription. The option to instantly undo an entire reconciliation is only available in the QBO Accountant version.

If you have an accountant, here's an article on the steps to undo transactions efficiently: Undo your client's reconciliations with QuickBooks Online Accountant.

If you want to proceed with correcting your previous reconciliation, you'll have to do it manually by following these steps to undo reconciled transactions one at a time if you prefer to do it yourself:

1. Go to the Gear icon, and select the Chart of accounts.
2. Find the account that has the reconciled transaction and tap View register.
3. Since the transactions are reconciled, you'll see an "R" in the checkmark column.
4. Select the box and keep clicking it until the box is blank. It removes the transaction from the reconciliation.
5. Click Save and proceed to the rest of the transactions.

For more details about the process, please refer to this article: Undo or remove transactions from reconciliations in QuickBooks Online.

Additionally, you can check out these resources as your guide to view various procedures that will help you reconcile your online transactions:

• Fix issues for accounts you've reconciled in the past in QuickBooks Online
• Learn the reconcile workflow in QuickBooks

We're always here in the Community to help if you have other questions about reconciling your accounts in QBO. Keep safe and have a great day ahead!