Updated 2015 MBP to High Sierra. I have a WD External USB 2 Hard Drive. When I connect to my MBP, it no longer mounts. Nothing on desktop or sidebar. Can see it under External in Disk Utilities, but it is greyed out. The drive is powered and I can feel it spinning in case. Shows in bar as USB External Physical Volume ExFAT. Not mounted. I have a Seagate with my iTunes Library on it, and it connects, no problem. Any ideas folks?