I even take the My Passport Ultra and it connects onto other Macs and PC’s with NO problem at all. I have tried attaching my phone, other devices and other HD’s to my macbook pro with no problem. It doesnt show up on my sidebar, or on disk utility.
For some reason My Passport Ultra SOMETIMES is not recognized on my mac (about 95% it is not recognized). So I have a MacBook Pro (Retina, 13-inch, Late 2013) 2.4 GHz Intel Core i5 8 GB 1600 MHz DDR3 running OSX Yosemite 10.10.1 I have purchased this HD (hard drive) back in July and have not had any issue until recently.