Ummm, after two years my MotoX 2nd Gen decided to quit on me? What the heck??
Sadly, electronics of all kinds sometimes die before we are ready for them to do so.
As a starting point, I suggest holding the power button down for what might seem to be an inordinate length of time (up to 2 minutes) to see if the phone might reboot. If uncertain about the phone’s charge status, stick it on its charger for a half hour before trying the preceding.