If Messages on your iPhone won’t send, shows green bubbles, misses conversations on one device, or stops notifying you, first identify which symptom you have. The fix often depends on whether the conversation uses iMessage, RCS, MMS, or SMS—not just on your iOS version. Apple’s current guidance covers general Messages troubleshooting; it does not establish a defect unique to iOS 18.5.
First: identify what is failing
Use the symptom that matches what you see. A missing alert is different from a message that never arrived, and a green bubble does not necessarily mean a message failed.
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- “Not Delivered” or a red exclamation point: troubleshoot sending and network service.
- Green bubbles instead of blue: check which messaging service is being used.
- Messages show up on another Apple device but not this iPhone: check the selected address, cellular line, and forwarding settings.
- A group conversation stopped arriving: confirm you are still a participant and check carrier-dependent group MMS settings.
- Photos or videos fail to send: check storage, attachment size, and image settings.
- No notification appears: check conversation alerts and Apple Watch routing.
Understand blue and green bubbles
Blue bubbles are iMessage. Green bubbles are messages sent using RCS or MMS/SMS. Green does not, by itself, indicate an iOS problem: the recipient may not be using an Apple device, iMessage may be unavailable or turned off on either device, or your settings may need attention after a new-device setup. See Apple’s explanation of green message bubbles.
| What you see | Service | Network and carrier considerations |
|---|---|---|
| Blue bubble | iMessage | Uses Wi‑Fi or cellular data. |
| Green bubble | RCS or MMS/SMS | RCS and MMS use Wi‑Fi or cellular data; SMS needs cellular service unless Wi‑Fi Calling is enabled. Carrier support and service can affect delivery. |
To check your iMessage setup, open Settings > Apps > Messages, make sure iMessage is on, then open Send & Receive. Confirm the phone number or email address you intend to use is selected.
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Fix a message that will not send
- Check your connection. For iMessage, RCS, and MMS, verify Wi‑Fi or cellular data is available. SMS requires cellular service unless Wi‑Fi Calling is enabled.
- Retry a failed message. If you see a red exclamation point or “Not Delivered,” check the connection and tap the alert, then choose Try Again. If it still fails and the option appears, choose Send as Text Message. Messaging rates may apply.
- Check the recipient details. Make sure the phone number or email address is correct. If only one recipient is affected, verify the address with them.
- Check carrier support. Ask your carrier whether your plan and service support the message type you are trying to send, especially SMS, MMS, or RCS.
- Restart the iPhone. If the connection and recipient details are correct but messages still fail, restart the device and try again.
Apple’s iPhone and iPad Messages troubleshooting guide covers these checks and related setup issues. If iMessage continues to fail, contact Apple Support. For SMS, MMS, or RCS delivery and feature-support problems, contact your carrier.
Fix messages arriving on one device but not another
- Open Settings > Apps > Messages > Send & Receive and select the intended phone number or email address.
- If your iPhone has multiple SIMs, confirm the cellular line you want to use is turned on.
- Install an available iOS update if your device needs one, then turn iMessage off and back on in Settings > Apps > Messages.
- If SMS messages arrive on your other Apple devices but not your iPhone, check Text Message Forwarding in the Messages settings on your iPhone and confirm the relevant devices are enabled.
These settings affect where messages are addressed and routed; selecting a different address can also make conversations appear split across devices.
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Fix group messages that stop arriving
First check whether you left the conversation or another participant removed you. Apple says a participant must add you back if you are no longer in the group. If you are still a member but the group has other problems, try starting a new conversation.
Group MMS also depends on carrier support and the relevant Messages settings. If the issue affects an MMS group, ask your carrier whether group MMS is supported on your service.
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Fix photos or videos that will not send
- Check available storage: low device storage can interfere with sending attachments.
- Consider size limits and upload time: carrier limits may apply to SMS/MMS attachments, and larger files can take longer to send.
- Try smaller image previews: if full-size images fail, open Settings > Apps > Messages and enable Send Photo Previews or Low Quality Image Mode, if available.
Fix missing Messages notifications
- Open the conversation, tap its name or icon, and check whether Hide Alerts is enabled. Turn it off if you want alerts from that conversation.
- If Messages is already open and active, the iPhone may not show a notification for every new message. Check the conversation itself before treating the lack of an alert as a delivery failure.
- If you use an Apple Watch, check where notifications are being routed. Alerts may go to the Watch or the iPhone rather than appearing on both.
For additional notification checks, see Apple’s Messages notification guidance.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Who to contact if the problem remains
Use the service involved to choose the right support route: contact Apple Support for a persistent iMessage or sign-in problem; contact your carrier for SMS, MMS, or RCS delivery, network service, or feature-support problems. Apple’s published steps are general Messages guidance, not confirmation that iOS 18.5 has a unique Messages defect.
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