[jyl]

Help. Stuck trying to replace OEM 128GB SSD in early 2015 MacBook Pro Retina 13" running High Sierra with a 480GB OWC Aura Pro SSD that is supposed to work with this model MBP.

Basically the problem is that I can't get Startup Manager.

I opened the MBP, removed the old OEM SSD, installed the new SSD, placed the OEM SSD in the Envoy Pro USB enclosure that came with the OWC kit, connected the USB enclosure to the MBP's USB port, and started when hold the Option key. I thought I'd see Startup Manager, boot to the old OEM SSD in the USB enclosure, then use Disk Utility to clone the new SSD to the old OEM SSD, then boot up normally from the new SSD.

However, I can't get Startup Manager. I only get Internet Recovery. I have reset PRAM and SMC, no help.

What's going on? Is the old OEM SSD in the USB enclosure somehow not bootable? Is there some security feature that is blocking Startup Manager?

If my only choice is Internet Recovery, what do I do? Install OS X on the new SSD from internet, then can I boot to OS X on the new SSD and use Disk Utility to clone the new SSD to the old OEM SSD? I vaguely recall some issue with using Disk Utility to essentially overwrite the boot drive.

I don't want to do a clean install because I don't want to spend hours reinstalling all my applications . . . I run High Sierra, Parallels, etc. I want to clone my OEM SSD.