How to remove customer profile editor app effects after uninstall?

Recently, we’ve installed this app:
https://apps.shopify.com/customer-profile-editor

This app changed our login interface.

Then, we removed it but the login interface is still there.

I’ve been looking for about a week and I cannot fix this issue. The app’s developers are no longer available to contact.

Also, I’m not sure if it’s something in my theme’s code.

My theme is eg. Theme 1.3. I have an older copy, Theme 1.1. If I preview Theme 1.1, the login is my login.liquid, it’s working. If I copy Theme 1.1, the Copy of Theme 1.1 will have the broken app’s login, which makes no sense. It’s just a duplicate, with no code changes in between.

Any updates?