Hi there
It seems like your messages is not activated. See this instructions on how to fix that
It might take up to 24 hours to activate iMessage and FaceTime. If the issue continues after 24 hours, follow these steps:
- Make sure that your device has the latest version of iOS or iPadOS.
- If you're using an iPhone, contact your carrier to make sure that you can send and receive SMS messages.
- Make sure you can send and receive SMS. If a prompt appears stating "Your carrier may charge for SMS messages used to activate FaceTime and iMessage", tap "OK" to allow possible SMS charges.
- Contact Apple Support.