Nice to have you in the Community forum, @Cman.
Great job in reconciling your accounts. I’m here to share with you some insights about how reconciliation works in QuickBooks Online (QBO).
Possible reasons for your QuickBooks Balance and Bank balance to differ is incorrect opening balance. This is the account's starting point you set when your first create it in your QBO account.
For more details about this, you can read through this article for guidance: Fix issues the first time you reconcile an account in QuickBooks Online.
Additionally, I’m adding this link that you can read to learn more about how reconciliation works in QuickBooks.
Know that you’re always welcome to tag me in your reply if you have any other concerns or questions about reconciling your accounts. It’s always my pleasure to keep you in working order. Stay safe.