While logging into Outlook on a mobile device, the log in process may break after authenticating with Okta Verify. This is caused by going home after the authentication process completes, while returning to the app you're trying to sign in to. To avoid this, it is recommended to switch between the apps, and avoid the home screen. The Apple support site provides an explanation and videos on how to switch between apps. You can find that site here.
If this does not seem to resolve your issue, please contact the Help Desk.