To fix the "iMessage needs to be enabled to send this message" error, go to Settings > Messages and ensure iMessage is toggled ON. Also, sign in with your Apple ID under Send & Receive. Restart your device if needed.
If you see “iMessage needs to be enabled to send this message,” it means iMessage is turned off. To fix it: go to Settings > Messages, then toggle iMessage on. Ensure you're signed into your Apple ID under Send & Receive.