The error code 9999 means there's a temporary disruption in the connection between your bank and QuickBooks Online (QBO), jkorn.
To begin with, may I ask which financial institution (FI) your checking account belongs to? Please know that this issue is temporary and is self-resolving. It stops new transactions from being downloaded into the platform and could last up to 48 hours.
Given the factors above, I recommend refreshing ↻ your bank's connection within QuickBooks after the specified time frame. You can also log in to your bank's website or contact their support team for updates on this temporary problem.
If the issue persists after 48 hours, I suggest clearing your regular browser's cache. Doing so helps eliminate outdated components that trigger common problems when using QuickBooks. You can also use another supported browser and Update the bank connectivity from there.
In the meantime, you can manually upload your bank transactions into QuickBooks if you need to manage your data urgently.
If you have more questions or need to provide more details about your concern, feel free to return to this thread.
