Getting logged out after redirect

Hello, I'm having an issue where my user is getting logged out.

I have a user flow where a user (not logged in) goes to endpoint: https://signup.website.com/my/endpoint

This endpoint creates a user and logs them in using Auth::login($user); and then it redirects the user (now logged in) to https://website.com/dashboard

But when they get to https://website.com/dashboard it says they are logged out.

If I do not redirect the user and leave them on https://signup.website.com/my/endpoint if I do something like if (auth()->user()) return "logged in"; it will show they are logged in, but any other subsequent page they go to on https://signup.website.com they will be shown as logged out.

We use .website.com on our session cookies and cross domain/subdomain auth is working just fine for the rest of our services.

Any ideas why this is happening and how I can keep the user logged in?

Thank you!