Auth0 doesn't work on mobile for regular web application (Flask app)

I have a Flask app that uses Auth0 (Regular Web Application type). It works perfectly on localhost and on Prod using a laptop. But it doesn't work on an iPhone or iPad.

When using an iPhone or iPad, it will show the Auth0 Login Page (just exactly like what it would show when using a laptop). However, when I try to log in either with Google or email/password, it would keep redirecting me back to the Auth0 Login Page (it doesn't behave like that when I use my laptop -- it would take me to my app). It does return an error Wrong Email Or Password when I typed in wrong credentials using either device.

Is there anything I'm missing for using Auth0 on a mobile device? I've tried both Chrome app and Safari, both behave the same.