Why is my new iPhone 16 not turning on?

To clarify, I have three times replicated the bad start condition by pressing and releasing the power button prior to the logo appearing. Each time it is then in the will not start condition until I use the up/down volume push sequence. That has always gotten the phone started but I do then have to wait a long time for the logo to appear (10-20 seconds). My previous dinosaur iPhone 8+ had no such issue. I didn't need to hold the power button longer than a second or two to start it after being powered down. My wife has an iPhone 15, and it also does not have this issue at all, just the iPhone 16. Given that they use the same software, I suspect an issue specific to the iPhone 16.

Randysea wrote:

Since I updated to iOS 18.2.1, the problem has not recurred. I have tried leaving my 16 plugged into the charger all night but turned off, fully charged but not plugged in, etc. Nothing triggers the problem.

Coincidence, sunspots, or ?? Anyway, I'm glad not to have any problem with my iPhone not turning on. Fingers slightly crossed, of course.

While it is called an iPhone, it is actually a very powerful pocket-sized computer that can incidentally make phone calls. And like all computers, it will crash occasionally, and that’s what happened. To minimize the probability of that happening it may pay to restart it occasionally→Restart your iPhone - Apple Support

And you don’t need to turn it off while it is charging; in fact, it’s better if you don’t. Continue charging overnight, and be sure to enable automatic backups.

Randysea wrote:

I did follow your instructions and upvoted them, too. It works but isn't a permanent fix to an ongoing problem.

When I got my replacement 16 Pro, I let it immediately update to 18.2. I've had two "not turning on" events since then. The second was this morning. Most of the time (in two weeks) it's started normally.

OK, so let’s check for other things that can cause iOS to freeze:

• Do you have any apps installed that purport to make your phone safer from hacking, an antivirus, an app that says it will speed up your phone, one that claims to “clean” it, or to manage memory?
• Do you have a VPN installed?
• Any apps that are “traditionally” unstable, such as Facebook or Facebook messenger?

AverageMick wrote:

When I called support they told me to update my software on my weeks new phone did that.

2 weeks later, it won't turn on with any number of learned truck tries.

• Press and quickly release VOLUME UP

     then

• Press and quickly release VOLUME DOWN

     then

• Hold the SIDE button until an Apple logo appears (15-30 seconds), ignoring "slide to power off" if it appears

The operative word here is QUICKLY; and try it a couple of times, the timing is a little tricky. If done correctly this will always work unless the phone has a hardware problem. 

I have an appointment at 1:40 this afternoon to have them diagnose my phone. This is the third time it didn’t turn on after charging it overnight.

Any resolution to the problem at your appt?

Every problem is a known problem.

You’re welcome! Glad I could help.

This worked for me. Thank you!

Why is that, Lawrence? I thought it was a good idea to turn it fully off at least once a day. Overnight seems like a good time. I keep it near my bed but turned off because I don't want it to ring or vibrate if someone calls in the middle of the night. In an emergency, I'd be reached on my landline. But I also want the mobile handy if I need it for some reason.

I have been turning my iPhones off nightly ever since my iPhone4S because Do Not Disturb doesn't block all the missing person alerts that go off here at least weekly in the middle of the night. They come blasting through anyway. The automatic backups happen at other times anyway.

I'd like to thank everyone for all the helpful hints and ideas. I can say that, once I succeeded in restarting the iPhone 16 Pro Max and installing the patch that was waiting, I have not had a single repeat.

My intuition is that there is a timing issue buried in the microcode on the chip that is compensated for by that last patch. Who knows? It might have been a bit hit by a random cosmic ray. I just recall that in my circuit design class (decades ago!) it was devilishly hard to guarantee a clean boot from a powered off state especially when there are billions of circuits on the chip. Propagation delay across the chip can be an issue that is hard to predict. I'll be happy if the repeat rate is below a few times/year.

The issue occurred the first night after purchase. There were a bunch of patches that loaded in quick succession after I got the phone home. There was one more that installed in the morning after I use the emergency startup sequence described above. I don't have a list of installed patches or that the patch actually helped with this issue. It may have been a coincidence. Either way, the issue has not reoccurred. At least now I know how to do a forced startup. The timing of the quick press sequence seems a bit sensitive though. It took me several tries before it worked. Pressing the volume buttons in the right sequence also seems important. Lawrence's advice is accurate. Slow deliberate pressing isn't fast enough, but "Flight of the Bumblebee" is too fast.

Whatever it's called, how do I get what Science Curmudgeon is talking about that fixes the problem?

I should note that I got my iPhone 16 pro directly from Apple less than two weeks ago, as a replacement under AppleCare for the same that I received and broke a few days before.

Randysea wrote:

Whatever it's called, how do I get what Science Curmudgeon is talking about that fixes the problem?

I should note that I got my iPhone 16 pro directly from Apple less than two weeks ago, as a replacement under AppleCare for the same that I received and broke a few days before.

Did you follow the instructions in the Top Ranking Reply near the top of this page?