Can't unlock Google Play achievements

I've played FC Mobile on and off, and I've recently noticed that none of the milestones I hit in game are registering the Google Play Games achievements? 

I initially signed up to FC Mobile with Google Play Games, and in the games settings it says it is linked. I don't see the "Welcome to Google Play" banner that pops up with other games when I boot them though, and it doesn't appear in my library within the Google Play Games app despite acknowledging that it's installed if I search for it. I'm stumped.