Battery Check; Power Reset; Restore Factory Settings - NIXON The Blaster User Manual

In the rare case that your speaker becomes unresponsive, press the small
reset Button using a pen to perform a hard power reset. It is located
directly above the micro-usB port.
reseT BuTTOn lOCaTIOn
(recessed button)
TIP: such unresponsiveness is typically caused by compatibility issues with
specific versions of mobile device operating systems. To avoid, make sure
your device is always using the latest software version.