Google Maps API, Location does not appear

I'm having a problem with the google maps API, everything was working fine when I was emulating my android studio map for my cell phone. After I make my app available in google play, the users that go down, the map does not appear for them, it looks like it has not set up "google_maps_key". I guess I'm doing something wrong by putting the app on google play. can anybody help me? I'm a beginner yet. If you need more information, I will already grateful