Hi Tommy_Gina,
welcome to the Apple (user-to-user) Community!
Re: "why cant i sign in to mobile bank app? : ... keeps timing me out"
Wondering if your iPhone 8 Plus has the newest compatible iOS 16 version:
Eg: About iOS 16 Updates - Apple Support says iOS 16.7.5 is the latest
"This update provides important security fixes and is recommended for all users".
You can check if an iOS update is waiting: Settings > General > Software Update
Note: It is a good idea to back-up your iPhone before you install any updates.
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If you already do have iOS16.7.5 installed, (ie: if no updates are waiting to be installed):
You may need to check (maybe with the bank?) whether the mobile bank app needs updating.
All the best :-)