The short answer
Work out which type is failing. Plain texts to one person point at that contact or a block. All texts failing points at your signal or your account. Picture messages failing while text works is mobile data or an APN problem. Blue messages failing while green ones work is an iMessage problem, not a network one.
Messaging failures feel identical from the outside and have completely different causes. Two questions sort them out: is it one contact or everyone, and is it text only or pictures too?
Read the pattern
- One contact only — a wrong number, a blocked number, or their phone is off. Try calling them.
- Everyone, all messages — signal, account or SIM.
- Text works, pictures fail — MMS needs mobile data even on Wi-Fi. Check data is on and APN settings are correct.
- iMessage fails, SMS works — an Apple service or internet problem, not your mobile network.
- Group messages fail only — group messaging is disabled, or one member’s number is causing the failure.
The fixes
Check signal, then toggle aeroplane mode
One bar is often not enough to send reliably even when calls connect. Turn aeroplane mode on for ten seconds and off again to force the phone to re-register with the network.
Turn mobile data on for picture messages
MMS is carried over mobile data, not over the voice network and not over Wi-Fi. If data is off or your allowance is exhausted, picture messages fail while plain texts continue working normally.
Check the message centre number
On Android, in the messaging app settings, there is a service centre number supplied by your network. If it is blank or wrong — which happens after switching SIM or network — nothing sends. Your provider can give you the correct value.
Reset the APN settings
Settings, Network and internet, SIM, Access Point Names, then reset to default. Incorrect APN settings break MMS specifically and are a common leftover after moving networks.
Turn iMessage off and on
On iPhone, Settings, Apps, Messages, and toggle iMessage off, wait 30 seconds, then on. It will re-register with Apple’s servers, which resolves most blue-message failures. Check that Send as SMS is enabled so messages fall back when iMessage is unavailable.
Delete very long conversation threads
A thread with thousands of messages and many attachments can cause the messaging app to fail or hang. Deleting or archiving old threads is a genuine fix that sounds unlikely.
Reseat the SIM
Power off, remove and refit the SIM, and check it is clean and seated. On an eSIM, check the line is still active in settings — profiles occasionally deregister after an update.
People who move from iPhone to Android and do not deregister iMessage often stop receiving texts from iPhone users, because Apple still routes those messages as iMessage to a phone that can no longer receive them. Apple provides a deregistration page for exactly this, and it is worth doing even months later.
Frequently asked questions
Why do my messages send as green instead of blue?
Green means SMS rather than iMessage — either the recipient is not on an Apple device, or iMessage could not be used, perhaps because one of you has no internet connection. It is not a fault by itself.
Why can I send texts but not pictures?
Picture messages use MMS, which requires mobile data and correct APN settings. Text messages do not. That is why one works while the other fails.
How do I know if someone has blocked me?
There is no reliable indicator, and apps claiming to tell you do not work. Messages appear to send normally. Repeated calls going straight to voicemail alongside unanswered messages is suggestive, not proof.
Will resetting network settings fix messaging?
Often, because it rebuilds APN and carrier configuration. It also clears saved Wi-Fi networks and Bluetooth pairings, so have your passwords ready first.
Establish which type of message is failing before changing anything. That one distinction points straight at the cause.
