A green text message on your iPhone isn't a sign that your phone number was
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.
Actually, iMessage not saying “Delivered” simply means the messages have not yet been successfully delivered to the recipient's device due to some reasons. Reasons could be: WiFi not working on iPhone/iPad or the iDevice don't have cellular data networks, they have their iPhone off or on Do Not Disturb mode, etc.
“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.
If your iPhone messages are green, it means they're being sent as SMS texts rather than iMessages. You'll always see green when texting Android users, or when you're not connected to the internet. If all of your iPhone messages are green, you should make sure iMessage is turned on in Settings.
If you see a green message bubble
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.
Check the Bubble Color
If you don't see a blue bubble on your end, then it's likely that they've blocked you on iMessage. It's important to note that this doesn't mean they have blocked your number altogether; it just means they have blocked you from sending them messages over iMessage.
For green messages, the texts that are sent are compatible with a wider range of phones and receiving services than blue iMessage texts. Since Android and other carriers operate within the SMS and MMS standards of text communication, these green texts are more versatile in who they can reach with their texts.
The blocked person also does not receive any notification that they're blocked. However, many iPhone users may be able to deduce that you've blocked them. This is because of the iMessage text “status” feature on iPhones.
If you see your messages green when they should be blue, it can be caused by either the receiver's device is an Android, or there is no Wifi connection available.
Blocking Someone on Android Messages and Apple iMessage
When you block a contact over Android or iPhone, they will still be able to send you text messages. These messages will not show up on your phone but the sender will see the messages as sent. They won't know that they've been blocked.
A green text message on your iPhone isn't a sign that your phone number was blocked, or that the text was not delivered. Instead, it means that the message was sent as a standard SMS message rather than an iMessage, which will appear as blue.
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.
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.
The Recipient Wasn't Using an Apple Device at the Time
Remember, iMessage only works between Apple devices. So, if your family or friend switches from an iPhone to an Android smartphone, for example, your iMessage will automatically be sent as a text message to them.
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.
When a message has been delivered, it has reached its destination and is stored in the recipient's inbox. The recipient can either read or delete the message at their convenience. After sending an SMS message, the service provider receives a notification confirming that it has been delivered to the recipient's device.
Call them. If you need to know, you can append *67 before the number you believe blocked you. This hides your phone number from the recipient, letting the call go through but listing the phone number as Private number, Blocked, or Unknown caller (essentially, you'll look like a spam call).
After you block someone, your messaging threads with them will remain in your Direct inbox, but you won't be able to message them. If you're in a group message with someone you've blocked, you'll get a dialog asking whether you want to stay in the group or leave.