I’m trying to do a clean install upgrade to Sierra on my 2010 MacPro. I’ve downloaded the installer to USB drive, and just trying to access Startup Manager via an Option key startup to start up in the installer.
Each attempt only delivers a blank screen, no startup manager.
I have tried:
Resetting PRAM and SMC
Tried both a Bluetooth and wired keyboard (same blank screen result).
I’ve tried multiple times with different key press timing.
The fact that it is not starting up correctly means it’s recognising the key press, but it’s just not going to startup manager.
Normal startup resumes if I press no key.