Currently, we have an on-going issue where users, like you, are unable to connect with your TSB bank account.
Rest assured that we've already informed our engineering team and they're in all hands working for a fix. I'd recommend contacting our Customer Care Support so you'll be added to the list of affected users.
Go to Help.
Select Contact Us.
Enter Unable to connect with TSB bank account in the What can we help you with? field.