I was updating the software and when it rebooted it was on the loading screen (after I log in) and then it just shut down. I've tried every trouble shooting tactic I could find online (safe mode included) and it's still not working. On boot-up I can see the grey apple, select my user, enter my password, the grey loader gets to the end, then it shuts down the computer.
MacBook Pro, iOS 9.2.1
Writing an effective Apple Support Communities question
Try this:
Boot the computer into Safe Mode, then restart normally. This will be slower than a normal startup.
Intel-based Macs: Resetting the System Management Controller (SMC)
Resetting your Mac's PRAM and NVRAM
Repair the Hard Drive and Permissions - El Capitan
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears.
Repair
When the recovery menu appears select Disk Utility and press the Continue button. After Disk Utility loads select the indented Macintosh HD entry from the the left side list. Click on the First Aid tab in the toolbar.. If Disk Utility reports any errors that have been fixed, then re-run First Aid until no errors are reported. Wait until the operation completes, then quit Disk Utility and return to the main menu. Select Restart from the Apple menu.
Now, Download and Reinstall OS X El Capitan 10.11.3 Combo Update.
MBP won't load passed login; turns off.
