Can I unreconcile a bank account.? I clicked Finish in error

Yes, you can unreconcile your bank account in QuickBooks Online (QBO), Janice.

We can undo a  reconciled statement by manually unreconciling each transaction. I’ll be more than happy to provide you with the steps:

1. Go to the Gear icon and select Chart of Accounts.
2. Find the appropriate bank, then click View register.
3. Select the transaction to edit.
4. Under the Check column, click the box repeatedly to change the status. ("C" - Cleared, "R" - Reconciled, and "Blank" - Not cleared or reconciled)
5. Click Save.

For more information about unreconciling, please refer to this article: Undo or remove transactions from reconciliations in QuickBooks Online

You may also consider looking for an accountant to Redo the reconciliation process.

Here's how to invite an accountant:

1. Click on the Gear Icon > Manage Users.
2. Go to the Accountants section and click Invite Accountant.
3. They will be asked to create a user ID before signing for the first time unless they already have an account with Intuit Business Services.
4. Until your accountant signs in, their status on the Manage Users page is "Invited." After accepting the invitation, their status changes to "Active."
5. Click Next and Finish.

You can also refer to this article for the detailed steps: Invite and add an accountant to your QuickBooks Online account.

If you have any further questions about unreconciliation, feel free to click the Reply button.