To reset / reboot your watch press the re-set button ( see number 5 below) with a pin. Then power on the watch by holding the silver button for about 3 seconds (see number 3 below).  It may take a few minutes for the watch to find the mobile signal if you are indoors or you may need to be at a window or outside for the watch to pick up the signal.  You will not lose any information or settings by pressing the reset button.