I have a new 4TB MyBook Studio that won’t mount on Yosemite. I have to unplug the USB and plug it back in for it to mount. When the computer sleeps, the drive won’t mount when awakened again without unplugging the USB and plugging it back in. I’ve updated to the latest firmware and the drive diagnostics check out. I’ve read elsewhere of people having similar mounting issues, and even that this is a known issue, but there are no fixes. I hope this isn’t true.
Hi mereman, welcome to the Community. We have passed this along to support.