Hi @avivk
I am sorry about the late reply to your inquiry!
From what I understand, once the user is redirected to the 3rd party URL, you are looking to implement Seamless SSO between those apps. The issue appears to be that your 3rd party app is a separate application which does not check if the user is registered with Auth0 or with your application.
Please review this community post, our documentation relates to OIDC SSO or this article regarding the matter.
If you have any other questions or found a solution to the issue, feel free to leave a reply or post again on the community!
Kind Regards,
Nik