Waiting for activation
Activation needs a connection — Wi-Fi or cellular — and the phone to be able to send a single hidden text to Apple. Check you are online, then check Settings → General → Date & Time is set automatically: a wrong date or time zone is the most common reason activation never completes.
Then switch iMessage off in Settings → Messages, restart the phone, and switch it back on. Activation can take up to twenty-four hours, but a fresh attempt on a good connection usually finishes in minutes.
Messages sending as green bubbles
A green bubble means the message went as SMS or RCS rather than iMessage. That is expected when the other person does not have an iPhone, and also when either of you has no data connection at that moment. It is not a fault on its own.
If messages to another iPhone user turn green consistently, check that iMessage is on for both of you, and that you are both online. If they recently switched to Android, their number may still be registered with iMessage — they can deregister it on Apple's website.
Check Send & Receive
Settings → Messages → Send & Receive lists the phone numbers and email addresses iMessage uses. Make sure your phone number is ticked, and that Start New Conversations From is your number rather than an email address — people who only know your number will otherwise receive your messages from an address they do not recognise.
If your number is missing or greyed out, sign out of your Apple Account in that screen and sign back in.
Message failed to send
A red exclamation mark means the message did not go at all. Tap it and choose Try Again, or Send as Text Message to fall back to SMS. If every message fails, toggle Airplane Mode off and on, then restart the phone.
If only one conversation fails, delete that conversation and start a new one — a damaged thread is uncommon but does happen, and a new one is a clean start.
Reset network settings
If nothing above helps and other internet services work, Settings → General → Transfer or Reset iPhone → Reset → Reset Network Settings rebuilds the networking configuration that iMessage relies on. It does not delete messages. See our network reset guide.
Updating iOS is worth doing at the same time — our update guide covers it.
When it is Apple
Apple's System Status page shows whether iMessage itself is down. If it is, nothing on your side will help, and messages are sent once the service returns. If it is up and nothing here has worked, Apple Support can see whether the Apple Account has an activation problem that needs their end.
Frequently Asked Questions
Why is iMessage waiting for activation?
Usually a wrong date and time, or no connection. Set Date & Time to automatic, switch iMessage off and on in Settings → Messages, and restart the phone.
Why are my messages green?
They were sent as SMS or RCS rather than iMessage — normal when the other person does not use an iPhone, or when either of you is offline.
How long does iMessage activation take?
Usually a few minutes, and Apple says up to twenty-four hours. If it has been longer, check the date setting and your Send & Receive addresses.
Does resetting network settings delete my messages?
No. It removes saved Wi-Fi networks, Bluetooth pairings and VPN settings. Messages, photos and apps are untouched.