There are several reasons as to why your new iPhone won't power on. First, is due to the battery that is completely drained or depleted. Another factor to consider is a software bug. While this is tagged among other hardware issues, power functions of your iPhone may also be affected by some software glitches. For example, a faulty app is causing the phone to power off and won't turn back on. Or worst, it could be due to a hardware problem like a damaged to pertinent components which needs to be repaired.
Considering the possible culprits, we therefore recommend the following workarounds. You can give these a try before visiting an Apple Genius for hardware check and/or repair.
First Workaround: Charge or re-charge your iPhone a little longer.Connect your iPhone to a charger and allow it to charge for at least two hours. You may say that you're certain that your iPhone is charged up, it is still better to make it more sure. There are instances that some third-party apps or certain processes in your iPhone system is causing the device to drain faster than you expected or perhaps, your charger or USB cable is not working. Having said that, it is worth checking again.
To isolate whether the problem is due to a faulty charger, try to use a different charger this time. If that works and the phone boots up, then you have to consider replacing your charger or USB cable. Otherwise, try the next workaround.
Also ensure that the battery is not damaged. While it may sound a bit odd for a new device to have a bad battery, it can happen sometimes.
Second Workaround: Perform a hard reset on your iPhone.Yes, it may appear to you that the device is not turning on but actually it is just frozen or showing a blank or black screen but is actually powered on. To hard reset your frozen iPhone, press and hold down both the Sleep/Wake and the Home buttons simultaneously for at least 10 seconds until the Apple logo appears. By then, let go of both buttons.
If you don't see the Apple logo no matter how hard you try or how many times you tried to hard reset, it is an indication that your iPhone won't reboot. In this case, proceed to the next workaround.
Third Workaround: Try to restore your iPhone SE/iPhone 7/iPhone 7 Plus.
This process is a bit harder than the previous ones. But I will try to make it simpler. Performing a system restore on your new iPhone requires iTunes or iCloud. To proceed with this workaround, I suggest going with iTunes.
Even if your iPhone is not booting up directly, it will still have to be functional to restore. You will need a computer with the latest version of iTunes installed to proceed with the following steps:
1. Connect your iPhone to your computer and open iTunes. Using a Lightning or 30-pin Dock connector is highly recommended.
2. Open iTunes on the computer and then click on the Device tab located on the upper-left of the screen.
3. Click on Backup.
4. Wait for the backup process to complete.
5. Click on Restore.
6. Wait for the restore process to complete.
If that works, then good. But if you are prompted with error or your iPhone cannot connect to iTunes, try the next workaround.
Fourth Workaround:Enter recovery mode.As what other users suggest, booting their device into recovery mode has helped them save it.
To enter recovery mode on your iPhone SE, 7, or 7 Plus, press and hold the Home button and Sleep/Wake button at the same time. As soon as the screen gets black, release the Sleep/Wake button. Keep holding down the Home button until you see the Connect to iTunes screen.
If you are using a Windows PC, it is also recommended to connect to a 32-bit Windows computer with iTunes. There are some cases where users who used a 64-bit Windows machine has found no help. Finally, restore your iPhone through iTunes (please refer to the previous workaround).
If all else failed, and you still end up with a new iPhone that is not turning on, it's time to contact Apple Support or your device carrier for problem escalation and ask for your other options.