Sign Out of All Devices on Xfinity Stream

I want to sign out of all my devices, and I spent 30 minutes on the phone with 3 different people and they led me no where. I don't have access to one device that still is logged into Xfinity stream and I don't want the person who now has access to the device to access my account. Why is this so difficult? Especially since others were helped on another similar thread. I am so frustrated that I am about to cancel my account.