Authorize URI for Different Users, Same Browser

I have integrated the RingCentral 3-legged OAuth flow in my application, but I am facing a problem. I am using the Official C# SDK.

1. UserA is asked to enter his credentials in a RingCentral branded pop-up window.

2. UserA is asked to Authorize the application.

3. UserA is authenticated.

4. When user logs out of my application, I call Platform.Logout().

5. UserB logs into my application, and initiate the Authorization flow, instead of going to step1 above, my user is taken to step2.

If I realize step 5 using a different browser, the user goes to step1 as expected.

How can I "reset" that RingCentral authorization window, so it always ask for login/username ??

Thank you.