Some of the most common delivery failures happen because the number is invalid, the recipient opted out of messages, there were network problems with the recipient's carrier, or your message contained content that carriers frequently block.
There are many reasons why aren't your message sending including your phone number is blocked or the DND list. Your text message is flagged as spam or contains illegal content or send to the wrong number or landline.
Your Message Is Flagged as Spam
If you are wondering why your texts aren't delivered to a certain person's iPhone, your text message may not have been delivered because it was flagged as spam by the recipient's phone or mobile carrier.
“The last message that you know was received and responded to…should have a 'delivered' status,” Lavelle explains. If, under the messages you've sent after that, you don't see that “delivered” notification, that could mean that person has blocked you.
If you send a message as a regular SMS in the green text bubble and you do not get a “Delivered” notification but instead get a notification similar to “Message not Delivered” or no message at all, that means you were probably blocked.
There are several reasons for this: The person that you sent the message to doesn't have an Apple device. iMessage is turned off on your device or on your recipient's device. To check if iMessage is turned on for your device, go to Settings > Messages > iMessage.
Send them an SMS message
When you send them an SMS and you get the "Delivered" notification underneath it, you weren't blocked. If you get a notification like "Message Not Delivered" or you get no notification at all, that's a sign of a potential block.
Messages that are sent or received won't be delivered. Also, the contact won't get a notification that the call or message was blocked.
When someone that you've blocked texts you, their texts go nowhere. They won't receive any notification that they're blocked, and their messages will still look like they've been sent. But you won't receive any of them, and you can't respond.
Delivered means delivered. If your message has been blocked, you will never know unless the recipient tells you you are blocked. The only difference may be if their device was set up to send Read Receipts, if it suddenly just starts saying "Delivered" that means they either blocked you or they shut Read Receipts off.
If you make a call and receive an automated message along the lines of “the customer is unavailable,” that person's wireless carrier may have blocked you. The messages can vary, but the result is the same. Your call won't go through.
Method 4: Check the Color of the Text Bubble
If you have text message fallback enabled, your device will resort to sending the message as a text, meaning the bubble will turn green after someone blocks you. If you are not blocked, then the bubble will turn blue.
A green bubble could also indicate that someone blocked you, especially when the bubbles have always been blue. When blocking occurs, iMessage sends your text, but the recipient never receives it. Your old messages remain blue, but the latest texts you send after they've blocked you turn green.
A green bubble could also indicate that someone blocked you, especially when the bubbles have always been blue. When blocking occurs, iMessage sends your text, but the recipient never receives it. Your old messages remain blue, but the latest texts you send after they've blocked you turn green.
Android phones move all blocked messages into a folder on the phone called “Spam and Blocked.” That means that the phone is still collecting messages from the blocked people; they just aren't notifying you.
When someone you've blocked tries to text you, you will not receive text messages from them. The blocked person also does not receive any notification that they're blocked.
Give them a phone call
Next, you could try calling the person. If the call goes right to voicemail or rings once (or a half ring) then goes to voicemail, that's further evidence you may have been blocked.
Messages that are sent or received won't be delivered. Also, the contact won't get a notification that the call or message was blocked.
Check the Bubble Color
For example, if you send me a message and I receive it with a green bubble, this means that the message was sent through SMS rather than iMessage. If you don't see a blue bubble on your end, then it's likely that they've blocked you on iMessage.
Delivered means delivered. If your message has been blocked, you will never know unless the recipient tells you you are blocked. The only difference may be if their device was set up to send Read Receipts, if it suddenly just starts saying "Delivered" that means they either blocked you or they shut Read Receipts off.
Take some time before you reach out to the person who blocked you. As tempting as it may be to reach out, waiting is usually a good idea. It's totally natural if you're wondering what went wrong. However, you're probably not going to get answers now—especially if you and the other person are both upset.
once you have blocked someone you can not call or text them and you can not receive any messages or calls from them either. you will have to unblock them to contact them. once you have blocked someone you can not call or text them and you can not receive any messages or calls from them either.
Blocked text messages disappear
When someone that you've blocked texts you, their texts go nowhere. They won't receive any notification that they're blocked, and their messages will still look like they've been sent. But you won't receive any of them, and you can't respond.