Hey there, @WWMarket. Thanks for joining the thread.
Our engineers are currently aware of some issues with Flagstar Bank and are working with them to resolve it. I recommend getting in touch with our QuickBooks Online Support Team so that you can be added to the list of affected users and you can get email updates as we find out more information. Here's how to contact them:
Let me know if you have any additional questions. I'm here to help. Have a good one!