Scroll down and tap (on newer iOS versions) or just Messages . Tap Blocked Contacts . Find the contact or number you want to unblock. Swipe left on the number and tap Unblock . How to Disable Message Filtering
If you are seeing the "Message Blocking is Active" notification or realizing you aren't receiving texts from specific people, you aren't alone. This issue can range from a simple setting you accidentally toggled to a more complex carrier restriction.
The most common reason for not receiving messages is that a specific number was accidentally added to your blocked list.
Go to Settings > Apps > Messages > Blocked Contacts . Swipe left on the number and tap Unblock .