New iPhone SE Touch ID

I currently have a 5s, iPad and also a new SE. All use the same apps, including a banking app. Touch ID works on all my devices fine... except the banking app on the SE. In the app there is a switch to turn on Touch ID but it wont stay on, as soon as you exit the page it defaults to off so TouchID will not work on the SE app. But it works on the other devices. Have reinstalled app several times to no avail. Touch ID is enabled on the iPhone SE and works with everything else. Is there some mysterious master switch in the SE's settings that is blocking this app for Touch ID? The bank reckons their app is not at fault. Any suggestions? thanks.