There are several things you can try to fix the startbutton... some work for some people, others work for others... if after doing all this, it still doesnt work... complain to Sony for making a horrible UI system...
- /show_window MainHUD.Inventory
- /hide_window MainHUD.Inventory
- alt+~ (if your start button disappears when you push this, you did not install correctly)
- delete username_server_uisettings.ini