Did a macOS upgrade do damage?
I thought my MacBook Pro was upgrading well to High Sierra, but it seemed to lock up with 43 minutes to go. I held the power key until it shut down, but now it won’t start up without showing a kernel panic notice and restarting again. Has the Mac been damaged?
Interrupting an upgrade, even if it has currently ground to a halt, could stop it part way through an EFI firmware update, or while replacing key files. It has clearly left your Mac in an unstable condition, so shut it down, connect the power adapter, remove all nonessential peripherals, then start up in macOS Recovery (see bit.ly/mfrcv).
If the Mac was updating its firmware, this should allow it to self–repair, although MacBook Pro models from 2016 onwards don’t make any sounds to inform you that this is happening. Once in Recovery, open Disk Utility from the initial window, and run the tool’s First Aid feature on the Mac’s startup disk. The Mac may then work fine, but you’re likely to have to install macOS over itself (see Recovery’s initial window), before the system will run normally, and sometimes may need to run Recovery over the internet (see bit.ly/
mfintrcv for different shortcuts for this, and the macOS version each will install). If those fail, try resetting the SMC ( bit.ly/
mfrstsmc) and NVRAM ( bit.ly/mfrstnv). But, you’re probably going to have to take your Mac to a Genius Bar or service provider to fix. Damage is unlikely, but there’s a small possibility it will have coincided with a hardware issue, which could have halted the upgrade in the first place.