MacBook Pro unable to startup from APFS
Late 2013 13” MacBook Pro A1502 running Mojave on 500GB SSD (formatted HFS+) has been running flawlessly for years. Decided it was time for the Catalina upgrade. Made backup, connected the A1502 to a MacMini, reformatted SSD to APFS using Disk Utility and installed Catalina. Verified drive with Disk Utility, all good, shutdown and disconnect the MacBook Pro from the Mini.
After normal POST tone, machine started up to a blinking question mark.
Bad drive? Repeated the whole process using a second Apple SSD = same result, blinking Q.
Repeated process using Mojave this time - format APFS, install Mojave - startup was a blinking Q.
Put the first APFS/Catalina SSD back into the 13” MacBook Pro, connected it to the Mini, set startup to the notebook, and the MacMini booted from it as it should with no problem.
Put that same APFS/Catalina SSD into a 15” late-2013 A1398, startup and ops were normal.
Back in the 13” A1502, startup was again the dreaded blinking Q.
Finally reformatted 2nd SSD back to HFS+, installed Mojave, put it into the 13” MacBook Pro A1502, startup and ops were perfectly normal and I’m back where I started many, many hours ago.
What possible defect could prevent APFS from startup and still allow HFS+ to operate normally?
(BTW, cannot upgrade from Mojave to Catalina with installer unless drive first has APFS format.)
Has to be a hardware issue in the A1502, no? Refuses to startup with drive connected externally, too.
If anybody can tell me what I'm missing, please do - I'm stumped. Thanks!