Unable to sign into Chewy and Harris Teeter apps on iPhone after iOS 18.3 update

I have an iPhone 15 Plus. I have downloaded shopping apps for Chewy.com and Harris Teeter (grocery). They both worked just fine (able to load properly and able to sign in without difficulty)....until I updated the iOS to 18.3. My other shopping apps (Walmart, Amazon, DoorDash) still load and work perfectly.

However, these two apps will not allow me to sign in. The app opens and I am able to use it without signing in, but when I try to sign in to my account for these two apps, the screen is blank and will not even give me the sign in screen. I have tried deleting/reloading both apps multiple times. My phone has plenty of memory, so that isn't a problem.

[Re-Titled by Moderator]