Need help with My Passport drive not mounting

My Passport drive won’t mount on MacBook Pro.

 I have tried Disk Utility.  It says it repairs, but needs to “update bootable software?” and then it hangs.  I have never seen this message before on any drive.  Verify permissions is not an option in disk utility (greyed out) for this drive.  At one point, I got a message about enabling permissions, but I haven’t seen that lately.  Drive doesn’t show up on desktop, but Disk utility sees it.  Is it possible it is somehow locked and if so, how do I unlock it?

Also updated firmware and hoped that would help but no change after the update, disconnect, reconnect and reboot.

Tried SMART diagnostic software several times.  Quick smart passes.  Quick test hangs every time at 90%, and full media scan also hangs at 90% (running it again now). When starting this software, the drive shows as having nothing on it, but I think it is almost full (1T).  I have not purposely erased it and don’t think I did that accidentally either, but I guess it could be damaged. 

Also recently updated to Mac OS 10.8.5 Mountain Lion.  I can’t remember whether this started before or after I updated to Mountain Lion - around the same time, but when I was updating, I’m sure the My Passport Drive wasn’t connected.  

Please help! Thanks!

Hello,

Have you tried testing the drive with the first aid option on the disk utilities?

How to test a drive for defects or problems on a Mac