Why is isAuthenticated false for the first request?

I’m following Build a CRUD App with ASP.NET Core and Angular tutorial but encountered a problem.

When I navigate to my app as a user that’s not logged in, and login via Okta’s sign in, I get redirected back to my app which is what I expect. However, when I set a breakpoint in AuthInterceptor on if (!isAuthenticated) {, I notice that isAuthenticated has a value of false (not expected) rather true for the first HTTP request (for the second, third request or any later request this value is true).

Why is this value is false and not true for the first HTTP request? This is a problem for my application because this effectively strips out the bearer access token and my app is unable to authorize the user.