Allow me to provide share some information and help you get rid of the error so you can sync your TD bank account to QuickBooks Online (QBO), @MECINC. 

For security purposes, the system will need to pause for 60-100 min before you can attempt to reconnect your bank with QBO again. Otherwise, the system will trigger a security alert or reauthorization request on your bank.

When this happens I'd recommend reviewing your bank website and look for a security notification that you need to take action with or reach out to the bank support.

Once this is settled on your bank , you can reconnect and categorize the bank transactions.

 For guidance, you can check this article: Categorize online bank transactions in QuickBooks Online. 

In addition, I’ve added this article to guide you on reconciling your account in QuickBooks Online regularly to track your income and expenses accordingly: Reconcile an account in QuickBooks Online. 

If you need further assistance with connecting your bank or if you have other QBO concerns, please let me know by clicking the Reply button below. I’m here to help 24/7. Take care.