When trying to set up the app for the first time, I receive the error message “blocking active message.”
This issue appears to be due to a feature implemented by the TMobile network.
It is a free T-Mobile service that allows you to block messages to and from your phone, to help you avoid unwanted messages.
https://support.t-mobile.com/docs/DOC-1712
You can adjust the setting with T-Mobile and this should resolve the issue.