WD drive greyed out

My external drive has stopped being recognised by my Imac and although I can see it in Disk utility it is greyed out so that I can not verify the disk. Would be grateful if someone could tell me what to do


Please make sure the drive is not locked. 

Setting up security to lock or unlock a WD external drive with WD SmartWare Version 1.6.x and earlier 

If your drive is a desktop drive make sure it is plugged in directly into a wall outlet. Avoid any extension cords, power strips and surge protectors.