iMessage not working on phone

Welcome and thank you for reaching out. 🤗

First, try the following steps:

• Disable any VPN connections and restart your iPhone or tell Siri: "Restart".
• Learn how to update your iPhone to the latest version of iOS.
• Learn what to do if your iPhone won’t update.

Sign in issue:

Learn what to do → If you can’t turn on or sign in to iMessage.

Connection issue:

Learn what to do → If you can't send or receive messages.

Need more help?

• Contact Apple Support if you still can't send or receive iMessages
• Contact your carrier if you still can't send or receive SMS, MMS or RCS messages

Additional help:

• United States: 1-800-APLCARE.
• Contact Apple Support.
• Get Support.

Good Luck! 👋🏼😉

Smiliñ 😎 Brian | Community Volunteer

Hello~ Try the information below…

If you can't send or receive messages on your iPhone or iPad - Apple Support

Click on below and review…

If you can’t turn on or sign in to iMessage or FaceTime on your iPhone - Apple Support*

Also…

Contact Apple Support - Apple Support

~Katana-San~

Can you give us more details? Any error messages given?

Could you successfully activate iMessage?

If yes, and the the general troubleshooting steps do not work, you should contract the official Apple Support and ask them to look into your settings from their side.

If you can’t turn on or sign in to iMessage or FaceTime on your iPhone - Apple Support

Contact Apple Support - Apple Support

Also check this recent discussion about it:

Unable to activate FaceTime and iMessage … - Apple Community