WD MY Passport Ultra intermittently not mounting

I am trying to connect the disk to a new iMac. It was working fine on the old iMac plugged into a USB 1.1 port. Currently it seems to work fine when plugging into a powered USB 2 hub. If it plug it directly into one of the iMac’s USB 3 ports, sometimes it mounts and others it does not. When mounted it will sometimes spontaneously unmount. This is supposed to be a USB 3 device. Anyone else noticing this? Any ideas?

Hello pingle,

Maybe you should try contacting WD’s Technical Support about this.

To Contact WD for Technical Support