It doesn’t active and show green instead

Hi there MaryClara12,

If you can't activate iMessage on your iPhone, start with these steps to see if they resolve the issue for you:

Check your device settings

1. Make sure that you’re connected to a cellular data or Wi-Fi network. 

2. If you're using an iPhone, you need SMS messaging to activate your phone number with iMessage and FaceTime. Depending on your carrier, you might be charged for this SMS.

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

If that doesn't seem to help, work through the remaining suggestions in this support article to see if you're able to get iMessage activated on your iPhone: If you can’t turn on or sign in to iMessage or FaceTime - Apple Support

Also, if the messages are sending in a green text bubble instead of blue, it's likely related to the activation issue, but here are a few additional reasons why this could be happening:

If you see a green message bubble instead of a blue one, then that message was sent using MMS/SMS instead of iMessage. There are several reasons for this:

* The person that you sent the message to doesn't have an Apple device.

* iMessage is turned off on your device or on your recipient’s device. To check if iMessage is turned on for your device, go to Settings > Messages > iMessage.

* iMessage is temporarily unavailable on your device or on your recipient’s device.

* You might need to update your settings for Messages after you set up a new device.

You'll find this information here: If you can't send or receive messages on your iPhone or iPad - Apple Support

Take care.