The player that you open with https:/localhost:3000/ is cached on your browser. Whenever you start a game with this player, your local app will keep that information. To play again there are multiple things you can do:
Click on the Reset current session button in the top right to reset this player, and create a new game for this player to join.
Click on the New Player button in the top right to open a new tab with a different player (you will see tab with an id).
Go to the Players tab in the admin panel and retire players that have finished or cancelled.
The app will automatically ("hot") reload when save changes to the code.