Are you getting a 505 error while trying to install the Circle app?
This error occurs if you've previously downloaded T-Mobile's FamilyMode app on your device. Uninstall the FamilyMode app and then try again. You should be able to install the Circle app and proceed to set up your Circle!
Why did this happen?
We helped build the FamilyMode app with T-Mobile, and an interaction between the two keeps you from installing both at the same time on an Android device. A future update will resolve this. Until then, you must install one or the other!