What device are you using and with which version of Android? Bank apps will stop supporting older versions of Android as the security protocols start falling behind without being updated. For example - the app for my primary bank supports Android 5.0 and up.
Actually - i just checked my 4 banking apps (including credit cards), two say 4.4 and up, two say 5.0 and up...
If you need additional help or have more questions or details to share, please join the site so you can reply in this thread. See this link for instructions on how to join Android Central.