There can be a lot of reasons for this happening. There is usually a message letting you know whether you have to update your log in, enter a security question, or whether it's just a problem at the bank level that QBO or the bank will resolve with time. Take a look at the messages in the banking centre. It should tell you what the problem is there, and then you can trouble shoot more effectively. If it's at the bank level, you will just have to wait until they resolve it.
I hope that helps!
