Good afternoon kevin2581,
Welcome to the Apple Support Communities!
We'd like to help with the issue you are having with the Alliant Credit Union app on your iPhone 13. iOS 16.5.1 was released today (June 21), so you might want to update your iPhone to the latest version. Then, check to see if there is an update to the app that is compatible with the latest iOS software. If the issue persists, check with Alliant Credit Union to see if you can access your account via their website if the app is not working.
How to manually update apps on your Apple device
Take care.
Let us know what you find out.
Take care.