Updated iPhone six plus to 11.x.x and left it unused for approximately six weeks. When I attempted to power it up, it would not start. No screen, no sounds, no vibration—true brick.
No dropping or water was involved.
Will not power up with cable or hard reset.
See if anything in the link helps you: If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support
If no luck, you need to schedule an appointment at the Apple Store Genius Bar. Your battery may have simply bit the dust and through the rest of the year, Apple is offering owners of phones from iPhone 6 or above a battery replacement for $29.
See if anything in the link helps you: If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support
If no luck, you need to schedule an appointment at the Apple Store Genius Bar. Your battery may have simply bit the dust and through the rest of the year, Apple is offering owners of phones from iPhone 6 or above a battery replacement for $29.
The key question was what was the state of the battery when you left it unused for 6 weeks. It should have been charged to 50% and turned off. If it was not turned off and the battery ran down below zero % for an extended period the battery is completely dead. Lithium batteries cannot tolerate being completely flat.
Charge it for 1 hour with the wall adapter. Then hold the HOME and SLEEP buttons at the same time until something happens. If nothing happens after holding for 1 minute, and you are sure the power source and the cable are OK (they work with other devices), your battery is not only dead, it is shorted, so you won't even be able to start the phone when plugged in.
If it was left on then almost certainly the battery drained damagingly low over 6 weeks. The device would have auto shut down when the battery got very low, but left without charging, it would have continued to slowly loose charge and is likely no good now.
So yes, a simply battery replacement from Apple may revive it.
Have you tried leaving it plugged into a power source overnight?
Yes. I’ve tried plugging it in to different power blocks, with different cables, and into the USB port on my computer.
I have an appointment, but the soonest one was a full week later. I plan on taking it in, but am continuing to attempt to resolve the issue on my own.
I don't specifically remember, but it is at least possible if not likely it was on and ran itself down. If that is the case, will a battery replacement fix it?
iphone six plus bricked after prolonged disuse
