iPhone iMessage says "Not Delivered

Hello, I have an iPhone 17 Pro Max running the latest iOS version (26.3). My iMessage is not working. When I send a message, it says “Not Delivered.”

I have already tried:

• Signing out and signing back into my Apple ID

• Turning iMessage off and on

• Restarting my phone

• Resetting network settings

• Checking Wi-Fi and cellular data

My internet connection is working fine, but messages still do not deliver.

Can you please check if there is any issue with my Apple ID or iMessage activation?

Thank you.