Free Msg: unable to send message - message blocking is active

Let's start with:

• Are these messages, text messages or email messages?
• Do you run any type of message blocking apps on your iPhone?
• Is this issue with anyone you attempt to send messages to or just a specific one? If a specific one, are they blocking you?
• For SMS text messages, have you contacted your cellular voice provider to see if the issue could be on their end.

The message Free Msg: unable to send message - message blocking is active means what it says.

You’re blocked from sending.

Usually: you’re being blocked by the recipient, or your carrier is blocking some or all of your message access, or maybe there’s a service outage somewhere in the path.

What Apple suggests: If you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support (VN)

If you’re not likely to be blocked by the recipient, check with your carrier, and with the recipient.