Bank feeds not updating can be really frustrating, I'm going to try help you out as best as I can.
Have you tried selecting the manual update button at the top right of the Banking/Transactions tab?
Also, if it's a standard feed, you might want to try selecting the pencil icon, then edit sign in info - you would then re-enter your banking information there.
I would love to know more about your situation to better assist you, which bank are you with?
The whole system isnt working, I brought it to their attention on 17th March and engineers have been working on the problem ever since with no End date in sight.