If your device does not turn on, you can turn off Activation Lock using Find My iPhone on iCloud.com.
1. In Find My iPhone on https://www.icloud.com/find , click All Devices, then
select the device you want to erase.
If you don’t see All Devices, it’s because you’ve already selected a
device. Click the name of the current device in the centre of the toolbar
to access the Devices list, then select a new device.
2. Erase the device.
Because the device isn’t lost, don’t enter a phone number or message.
If the device is offline, the remote erase begins the next time it’s online.
You receive an email when the device is erased.
3. WAIT BEFORE YOU DO THIS STEP!!
When the device is erased, click Remove from Account. Wait for the
email confirming your device has been erased before removing it from
your account.
All of your content is erased and someone else can now activate the
device.
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