Hello, I have the following issue: I have a Late-2009 iMac 21.5 (Radeon Graphics) which died due to the common GPU failure issue. I still have it and the HD is intact so there is always that...however.... I had always backed up this iMac via Time Machine to a WD My Passport 1TB External, and never had any problems with the backups on that machine, i.e. I could always access archived versions of the system and recover files if needed. I think the OS was Yosemite when it died. I put the WD on the shelf and thought "Never mind, I'll be able to restore everything once I repair the iMac or buy a new one". Well 18 months or so went by and I've never been able to fix it, and lack of funds have prevented acquisition of a replacement until now, having bought a pre-owned 2010 MacBook running Sierra, which is just fine and meets my needs at a reasonable price. So of course the first thing I do is attach the Time Machine WD to the MacBook, restart it with CMD-R held down to initiate the recovery process, and hey presto.......nothing. The WD is spinning, the light is flashing, but the recovery app is not seeing it, it's not mounting on the desktop at all. I've brought the WD into work to plug it into my PC and ran the WD "Data Lifeguard Tools" app, both on a Quick and and Extended Test, and both tests provide a Pass. So, is it the fact that I'm trying to restore a Yosemite Time Machine Backup with Sierra, or is the MacBook not providing enough juice to the USB 3 WD Drive, or is there some other issue? All help appreciated.