VolodesiCould be that you need to setup chat features. I'm guessing your other device sends all messages as data and not SMS. In your messages app, press the three dot menu and then settings. After this press Chat features and enable everything
I've been using Google Fi on my phone since it came out and haven't had much issue. Google just recently announced that Fi was going to stop supporting Hangouts and I'd need to use Messages. But it can only seem to send messages but not receive.
I have tried completely uninstalling Hangouts and setting Messages to default, but it still can't receive messages. Also tried the Beta version of Messages with no luck.
Everything is updated to the latest.
Google Message's not able to Receive on Google FI