400 Bad Request when trying to logout by redirecting

Questions OAuth/OIDC
2

I have checked all following posts for reference & I have it all configured as its required, but still its not working:

  1. Configure Single Logout in app integrations | Okta
  2. Getting response 404 for OIDC Logout API call
  3. Logout fails with 400 bad request
  4. Logout 400 Bad Request (Logout URI already defined)