As a last resort, you can try resetting your iPhone to its default settings. This will erase all of your data, so make sure to back up your iPhone before doing so:
Carriers occasionally release small updates to improve connectivity. If you’re running an outdated version, it could cause messaging errors. Go to Settings > General . Tap About . how to remove message blocking on iphone
If none work, – they can see and remove carrier-side message blocks instantly. Apple cannot remove personal or carrier blocks. As a last resort, you can try resetting
If you see the specific error message "Free Msg: Receiver unable to receive message - Message Blocking is active," the issue is likely with your service provider (T-Mobile, AT&T, Verizon, etc.) rather than your iPhone settings. Go to Settings > General
Your plan might have reached its text limit.