See Troubleshooting Texting Issues . Are you using Google Messenger?
For Republic 3.0 Phones (Google Pixel and Pixel XL, Huawei Ascend 5W, Moto G4, G4 PLUS, and G4 PLAY, Moto X Pure Edition, Moto Z and Z PLAY, Nexus 5X, 6, and 6P, and Samsung Galaxy, J3, S6, S7, and S7 edge)
You’ll need to ensure that the Google Messenger app is installed and set as the default messaging app. While other messaging apps may work, we’ll only provide support for messaging using Google Messenger.
Note: The Moto X Pure, and all Samsung phones require the installation and configuration of Google Messenger.