Line not eligible.. Att call protect

@freeewilly

The earlier iphones are not HD voice compatible which is a requirement for Call protect. iPhone 6 and android phones running Marshmallow or newer OS should be HD voice compatible 

This is also why prepaid, which doesn’t have HD voice, cannot use Call Protect.  

If your phone is not eligible, download Hiya.   I have it on my non ATT phone and it works very well.

@Jeff91755 Do you know what family plan you are on? An old minute plan? Mobile Share ______? Unlimited Plus/Choice?

  Of course it works on newer iPhones.   It won't work on older plans, prepaid plans or if your phone isn't set up for advanced calling features.  

https://www.att.com/features/security-apps.html

Download from iTunes.  If you can't activate the app, it's something else.

I can at least confirm that it DOES work on an iPhone 6 Plus and 6S Plus as I’ve had it working on both. On an iPhone 5 I get the same message as you so I need to look into it more. 

I had the same problem and got it "RESOLVED"

If you're getting the error message, it's because your phone is not purchased from ATT.

I bought the international version of iPhone from Apple Store.  I called ATT and added this phone onto their system, I'm able to activate the Call Protect now.

It dosen't work because at&t makes money on the scam calls on prepaid and loses money on post paid accounts nomorobo can block them on exactly the same phone that at&t say's that it's impossible.