Problem on SSO Login

yes I have to enable login required for disallowed anonymous access.
I am explaining again
The following flow is executed for my website when I enable SSO login and set everything up for SSO login

  1. this is my main website. here a one community button ,when user click this button it will call mywebsite.com

  2. mywebsite.com call my community(discourse community) website login page. then user who logged in main website is automatically logged as in community website(when I disabled login required setting of community website). But problem is that when I enable login required then login page does not call automatically. I have to click login button manually then It will logged the community page.

So I need some way to call the login button(or page) automatically without disabling login required settings.

This is official SSO Documentation link