The most likely scenario — especially if your texts aren’t normally green when you correspond with the same contact — is that something is wrong with iMessage. This can be an issue with your app, the recipient’s app, or both depending on the situation.
- A connection to either cellular data or Wi-Fi is required for iMessage to work as intended, otherwise it will default to SMS. You may need to find a new (and trusted) network to switch to, or physically move to another location to find a stronger signal.
- Mismatched time zones can also cause trouble. Open Settings (the gear icon) and select General, then tap Date & Time to change it on your iPhone.
- You may have missed an iOS update, in which case you’ll want to open the Settings app (the gear icon) and select General. Then tap Software Update and download any updates that may be available.
- The iMessage app itself may need to be restarted, in which case you should open Settings (the gear icon), select Messages, then turn off the toggle for iMessage (it will turn gray). After which you can restart your iPhone and then turn iMessage back on in Settings.
If iMessage continues to send your texts as SMS, it’s also possible that the service itself is experiencing problems. You can check Apple’s official System Status page to make sure, and if it turns out iMessage is down all you can really do is wait.
