If you are blocked on iMessage by someone but you are not sure about it knowing it is necessary. Although, there are several valid ways which can help you with this query How to know if someone blocked you on imessage

It will also help you to decide whether you can continue trying to contact them or are moving on from that person.

Well, these key indicators are quite simple to acknowledge it. If you see a lack of delivered messages read the status beneath your last message. Additionally, green message bubbles showing instead of blue. Moreover, FaceTime or phone calls that either go to voicemail or don't ring.

If you see such instructions in your iMessage then it means someone has blocked you from iMessage. In such cases, you can also try reaching out through various other platforms to contact them.

Also, you can click the link provided above to find more accurate stepwise guidelines.