My Passport Ultra 1TB not Initializing

  I have a 2 tb WD drive that is more than half full of my Photography photos. I go to log into my iMac today and get a message that one of my drives failed to mount and gave me 3 choices - initialize (I can’t afforde to lose the data so this was not an option), eject (which I chose thinking I could remount it _NOT!), and ignore. 

 I’ve tried everything I can think of to get my computer to recognise the drive - no luck. I have a huge library of photo’s on this drive and I’m pissed off. 

  Has anyone come up with a solution to this problem? 

P.S. WD > Mac just had a major update which I udated yesterday - could that have anything to do with it?