Problem google maps api not shown map

The issue is as follows, finish making my application in the IDE of Android Studio, When emulating the app in the emulator or a physical device is all good, the problem arises when I generate the APK.

Now explain: Google maps is seen without problems to emulate, not so when generating the APK through Android Studio, it looks like it does not recognize the api-key bone is not reflected in the map and I do not understand why. .. It should be noted that you already use "multiDexEnabled true", also generate the SHA-1 fingerprint and the map still does not work.

<resources>
<!--
TODO: Before you run your application, you need a Google Maps API key.

To get one, follow this link, follow the directions and press "Create" at the end:

https://console.developers.google.com/flows/enableapi?apiid=maps_android_backend&keyType=CLIENT_SIDE_ANDROID&r=3A:64:19:43:62:19:28:63:12:A0:F2:39:79:F3:9A:05:1F:44:2F:51%3Bixtapa.com.mx.ixtapazihua

You can also add your credentials to an existing key, using this line:
3A:64:19:43:62:19:28:63:12:A0:F2:39:79:F3:9A:05:1F:44:2F:51;ixtapa.com.mx.ixtapazihua

Alternatively, follow the directions here:
https://developers.google.com/maps/documentation/android/start#get-key

Once you have your key (it starts with "AIza"), replace the "google_maps_key"
string in this file.
-->
<string name="google_maps_key" templateMergeStrategy="preserve" translatable="false">
    AIzaSyDAgFUrcH2olG29IUClfIrSgqH4-wZ0AL8
</string>

Class of the Map

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {

private GoogleMap mMap;
String lat = "";
String lon = "";
String Name= "";
String Address="";



int latI;
int lonI;
Double latD2, lonD2;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);
    // Otain the SupportMapFragment and get notified when the map is ready to be used.
    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
            .findFragmentById(R.id.map);
    mapFragment.getMapAsync(this);


    Intent i = getIntent();
    Bundle extra = i.getExtras();




    if (extra != null) {
        lat = (String) extra.get("Lat");
        lon = (String) extra.get("Lng");
        Name = (String) extra.get("Name");
        Address = (String) extra.get("Address");
    }
        //Toast.makeText(this, "Se recibieron los valores", Toast.LENGTH_SHORT).show();
        //Toast.makeText(this, lat + lon, Toast.LENGTH_SHORT).show();
    else {
        Toast.makeText(this, "No se reciben valores", Toast.LENGTH_LONG).show();
    }


    latD2 = Double.parseDouble(lat);
    lonD2 = Double.parseDouble(lon);






}


/**
 * Manipulates the map once available.
 * This callback is triggered when the map is ready to be used.
 * This is where we can add markers or lines, add listeners or move the camera. In this case,
 * we just add a marker near Sydney, Australia.
 * If Google Play services is not installed on the device, the user will be prompted to install
 * it inside the SupportMapFragment. This method will only be triggered once the user has
 * installed Google Play services and returned to the app.
 */
@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;

    // Add a marker in Sydney and move the camera
    LatLng Hotels = new LatLng(latD2, lonD2);
    mMap.addMarker(new MarkerOptions().position(Hotels).title(Name)
            .snippet(Address)
            .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_CYAN)));
    mMap.moveCamera(CameraUpdateFactory.newLatLng(Hotels));

    mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(
            new LatLng(latD2, lonD2), 12));


    mMap.getUiSettings().setZoomControlsEnabled(true);



    if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        // TODO: Consider calling
        //    ActivityCompat#requestPermissions
        // here to request the missing permissions, and then overriding
        //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
        //                                          int[] grantResults)
        // to handle the case where the user grants the permission. See the documentation
        // for ActivityCompat#requestPermissions for more details.



        return;
    }
    mMap.setMyLocationEnabled(true);

}

}