I have a mid-2014 15-inch MacBook Pro Retina. I was using it half an hour ago, and everything worked perfectly. I turned it off and left it for five minutes or less. I turned it back on to check something I forgot, and now it won’t boot. the little progress bar underneath the Apple logo fills in much slower than normal, and the computer turns off when the progress bar is about 2/3 full.
Battery is fine. The computer was plugged in before I turned it off, so the battery is full, and it’s plugged in now.
I have a Windows partition I can boot from with no problems since the Mac problem started.
Trying to start in safe mode results in either a black screen indefinitely or the computer turning off when the progress bar is maybe 1/10 full.
Trying to start in diagnostics mode results in a black screen indefinitely.
Tried resetting the system management controller. Nothing changed.
Tried resetting the PRAM. What happened is the Mac kept restarting every five seconds or so while I kept cmd+alt+P+R held down and then returned to the above problem when I let go.
If it helps, the internal SSD is a 960-GB Aura drive with two partitions: 760 GB with Catalina and 200 GB with Windows 10. It is not the internal drive that came originally with the Mac, but the replacement was made several years ago and I’d never had a problem with it before.