Thank you for reaching out to the Community. Allow me to help share some updates about the Banking Error 9999.
The error 9999 is a reported script error that interrupts the connection between your bank and QuickBooks Online. Our engineers are currently investigating the occurrence of this error and are working on the fix of this unexpected behavior.
Also, I recommend reaching out to our Customer Care support. They have the tools that can add you to the affected user's list. This way, you'll receive an email directly from our engineers once updates are available, or once the issue is resolved.
Let me share the update with the 9999 error with TD Bank, @thedishman.
I've checked our records and found out that the TD Bank error 9999 has been resolved and our engineers said this is working as designed. Quickbooks Online customers with connections to TD banks in Online Banking will be limited to 1 manual update request within 5 minutes.
In case you initiated additional requests within the 5 minute limit, after the first update for the same login credentials, the Error 9999 will appear. This limit is to help ensure that Intuit customers are not contributing to increased traffic at the bank servers through multiple manual update requests.
However, since you still experiencing this error within two days, I'd suggest contacting our Customer Support Team. They can further investigate this matter for you. You can follow the steps shared by my colleague above on how to reach them.