So I have a older Mid 2012 MacBook Pro an I can't get it to boot any drive. Only Network recovery can be booted into. Cannot boot from the internal SSD, nor a bootable external drive over USB. Not even the SuperDrive shows up in disk utility in network recovery. Both drives are in working order and can be accessed on other Macs without issue. I would suspect the SATA cable but it doesn't explain why I can't boot over USB either. I'd try FW800 but lost my cable somewhere. Any thoughts?