Windows Integrated Authentication will not support Reactive Web app & will not allow users to login directly inside the application even though SSO[Single Sign On is enabled in the Environment] This component can be used has a redirector to login into the Reactive app.

https://success.outsystems.com/Documentation/11/Developing_an_Application/Secure_the_Application/End_User_Management/End_Users_Authentication/Integrated_Authentication

About the component: Each time when the application is not detecting the user it will redirect the user in backend to a Traditional application[Since WIA support Traditional app] & there the user gets logged in and again redirects to the reactive app.

The bellow settings should be enabled in service center & Lifetime[Target environment configuration]

1. Enable HTTP Strict Transport Security(HSTS) [Service center -> Environment configuration -> Environment Security -> Secure Connections]
2. Force HTTPS for screens in Web Applications [Service center -> Environment configuration -> Environment Security -> Secure Connections]
3. Cookies -> Secure[Service center -> Environment configuration -> Environment Security -> Secure Connections]
4. Single Sign-On Between App Types [Service center -> Environment configuration -> Environment Security -> Application Authentication]

Note: If your environment is mapped with Lifetime you can find the first 3 points under LT -> Infrastructure -> Environment security[Target env]

OS will fix this issue in future release, developers can utilize this component until we get a new release which fix this issue.