Available Devices is in the Spotify client - see this article for more information about Spotify Connect.
Clicking on each session removed them from the Devices list. If you can't open the web player, you might need to do it through another client, such as mobile Spotify.
I had this issue too, but it's no longer happening to me like that. Have you tried logging out and back in? (you can do it on spotify.com website if the web player remains inaccessible).
Let me know how you get on 🙂