launch ASWebAuthenticationSession from single sign on extenstion

I need to launch ASWebAuthenticationSession from single sign on extension, but its not launching it might issue with anchoring window, I have create custom windo and passing it in presentanchor(for session) function, custom window is launching but ASWebAuthenticationSession browser is not launching

Note - flow is like this

1. Apple PSSO register window lauched
2. OIDC login will happen via ASWebAuthenticationSession to get accesstoken which will use in device registration

but ASWebAuthenticationSession is not launching, I am using custom scheme as redirect URI

iskeywindow for custom window is always false

what is right approach to achieve the goal