Issue with IDP as it is again asking Username

HI Team,

I have an OIDC app that should authenticate corporate users from another tenant .
Users will be asked Username and if user is an external user (non-corporate), he will be directed to sign in form okta as those users reside in Universal Directory.
For corporate, federation is done.
App is created at the identity provider as well. They have created another authorization server for our requests.
In my okta tenant , I created an IDP and updated all fields like authorization/token endpoint etc. Authentication is happening from the IDP and user gets redirected to landing page , but within a span of second user is redirected to my app login page. It asks me for the username again . If I provide username, it is redirected to my landing page.