There are two ways to return your wireless Bluesound Player to Hotspot Mode other than a factory reset.
Via The App
In the BluOS Controller App, open the Help Menu from the Nav Drawer (or Configure Player from the Player pull-down menu in the BluOS App for Windows or OS X). From the Diagnostics page, select Force Hotspot Mode located at the bottom of the page. This will immediately erase the currently saved wireless configuration and send the Player to Hotspot Mode.
Moving the Player
If your current configured router is not in range whether by being turned off or your Player moved to a place out of range, a BluOS Player will try to reconnect for 5 minutes to the configured router. If the router cannot be found after 5 minutes, the Player will return to the default Hotspot Mode.