WD 3T Essential not mounting

I have been using my WD 3T hard drive on my imac for almost a year using (os mac extended journaled).

Suddenly it is no longer mounted and won’t mount.  I can see through the top that it is lighted but an external hub  no longer shows it’s glow light so I gather it is not connecting with the Mac.  I have been using it directly connected to the imac not through the hub.  I have switched USB cords but neither the disk utilities nor Disk Warrior  can recognize it.  Your thoughts please. 

Have you tried using another power supply?