Why does iMessage activation on iPhone 7 Plus always fail?

If you get an error when trying to activate iMessage or FaceTime

To use iMessage or FaceTime, you need to activate them on your iPhone, iPad, or iPod touch. If you see an error message during activation, follow the steps below.

When activating iMessage or FaceTime, you may see any of the following messages:

Waiting for activation

Activation not successful

Activation error

Unable to log in. Please check your network connection

Check your device settings

Make sure you are connected to a cellular data or Wi-Fi network. If you're using an iPhone, you'll need to activate your phone number via text message for use with iMessage and FaceTime. There may be a charge for this text message depending on your carrier.

Go to Settings > General > Date & Time and make sure your time zone is set correctly.

Turn off and restart iMessage and FaceTime

Go to Settings > Messages, and then turn off iMessage.

Go to Settings > FaceTime and turn off FaceTime.

Restart your device.

Reopen iMessage and FaceTime.

Still not activated after one day?

It may take up to 24 hours to activate iMessage and FaceTime. If the problem persists after 24 hours, follow these steps:

Make sure your device has the latest version of iOS.

If you have an iPhone, contact your carrier to make sure you can receive text messages.

Contact Apple Support.

Reference materials

Apple.Apple[cited on 2017-12-29]