It is possible the SSD is failing and this page has a number of possibilities and solutions. First of all I would run diagnostics. Restart the system and when you do start tapping F12. Select full diagnostics and watch for any drive errors. Are you having any other problems like the system not holding the dat and time? In that case the CMOS battery could need replacing. You can also try removing the battery (information here) for at least 15 minutes then reinstall and see if the drive is detected although it is not an easy task getting to the battery.