Macbook air 13' 2017 not powering on after update

I understand your Mac will not power on following a macOS update.

Begin with If your Mac doesn't turn on. That gets some preliminary steps out of the way.

Read and follow each of its steps, including all the links within it, all the way through and including Step 4, which directs you to:

If your Mac starts up to a blank screen

Read and follow each of it steps also, all the way through and including the end, which takes you to:

"If you still need help, please contact Apple Support."

I understand. That's all you can do, although anecdotal reports indicate multiple persistent SMC Resets sometimes result in success.

Let me lay out my sequence of events. This may or may not be helpful for you, but here goes. The bottom line for me is that this problem *apparently* resolved itself.

I always update *manually*. I get notifications, but choose to update only after creating a bootable image. In this case, the image didn't help, because my machine (2017 27" iMac 3.5 GHz i5, 24 GB RAM, 500 GB SSD) was BRICKED, and so could do NOTHING. I tried booting into the recovery partition. No joy.

So, here's the sequence of events. After creating my disc image, I successfully downloaded the update (3 GB), and fired off the update. It started normally (Apple logo and "thermometer" indicating progress), and I left it and went running and shower. 3 hours later I came back and tapped on the spacebar. NOTHING. Pressed the power button. NOTHING. Press and hold the power button. NOTHING. Unplug the power (SMC reset). NOTHING. Tried booting into recovery partition (option-R). NOTHING. Went through this cycle at least 3 times, including de-powering for 5 minutes. NOTHING ^9.

So, I left my computer and went to my wife's office to use her computer (mine is a BRICK, right?). Tried support "chat". Got dumped. Called US tech support (1-800-275-2273) got in the queue. Waited 20 minutes. Still in queue. Walked past *my* office and notice that my computer had revived itself (?!?!?) and had resumed updating. Watched it complete the update just as the tech support guy finally got to me. I told him what had happened, thanked him for his time, and hung up.

Between my wife and me we have bought 4 iMacs. 3 have been fine and still work great (although are unsupported..) My current iMac was *never* right from day 1. In the 32 months I have owned it, it has been fine 99.9% of the time, but every once in a while it has one problem or another. One Safari update killed Safari. Twice now, 18 months apart, updates have completely bricked it.

Simply put, I think there is a hardware problem somewhere, and when all the planets are aligned perfectly, something breaks. In this case, I think that the update procedure HUNG (which is to say there is a logic race condition somewhere and the program is waiting for a response that never comes), but there is some very long time-out (30 minutes?) that gets triggered when it hangs, and after the time-out it tries again. Further, my *guess* is that this time out is built in to deal with slow internet connections (mine is fast) and/or power interruptions during update (my machine is on a UPS, and the power was never interrupted (except when I physically unplugged the machine). Of course, your laptop *is* a UPS.

If your machine is "new" I would take it back and ask for a new one. My machine has spent a total of well over 8 days in the Apple shop, and nothing useful was accomplished. The "geniuses" are, in reality, not all that smart. And, furthermore, a problem this subtle and this intermittent is *never* going to be found and fixed.

So, in a situation like this, it is time for Apple to suck it up and do the right thing. You pay big bucks for it to "just work", and when it is new and doesn't just work, Apple needs to do the right thing, and take the defective merchandise back and give you a new one.

Just my opinion.

Best of luck.

Just noticed that your Mac is a 2017. So, not "new". Oh, well. Which processor is it? Mine is Core i5 7600. This is the middle of the Core i5's that were offered. I have often thought it was a mistake to get this processor, since there are probably very few sold, and I wonder if there are certain "corner cases" where the software is just not properly tested on the Core i5 7600.

I'm afraid I have to agree with John Galt. Your only chance is to mindlessly keep resetting the SMC and hope for the best.

Same thing here. The 10.15.6 update KILLED my iMac!!!!

At least that's a visual indication the SMC Reset was effective. The LED state change does not occur on all Macs, even if the SMC Reset worked.

Hope this helps someone else in this situation.

Good! Me too.