Logout from subdomain does not logout from the domain


We’re using Auth0 SSO both for our App and Onboarding.
Our app is at somedomain.com, and our onboarding is at onboarding.somedomain.com.
They are both using the same tenant.
After successful login to the app, if the user hasn’t completed the sign up process, it gets redirected to the onboarding subdomain to complete it.
The login redirect works perfectly with the custom domain, but we’re having trouble with the logout.
When the user requests to log out while using the onboarding app, isAuthenticated equals false, but in the app - isAuthenticated equals true, though it shouldn’t.

I would love to understand how I enforce the logout to affect both the app and the onboarding.