Android : Map not show on release Android app

I have developed a Android app, this app use Google Maps. On debug version I can see the map but in release mode I cannot see the map only a gray box.

To generate the release version I have use Android Studio (0.8.2) and I follow these steps:

1. On Android Studio I have use "Build" -> "Generate Signed APK" to start the wizard APK generation;


2. From the wizard I have generate my release keystore (jks file) then I have generate the APK;


3. I have use the release keystore with the comamand "keytool -list -v -keystore myreleasekeystore.jks -list" to get SHA1 code;


4. On Google API Console, under "Apis & Auth" -> "Credensials" on "Public API access", I have change "Key for Android applications" to add a new line like "mySHA1codeFROMrelaseKEYSTORE;nameOFmyAPP", so now I have 2 line (one for debug and one for release);


5. I don't have change the API KEY on my app because is always the same;


6. I have upload the app on Google Play, I can download and install it but I cannot see the map;

This is the error on log: "Failed to load map. Error contacting Google servers. This is probably an authentication issue (but could be due to network errors)."

I have also try to generate a new API KEY, replace it on app and regenerate the Signed APK but I get the same result.

I do not find errors in my approach, I read a lot of articles on the internet about this.

Help me because I'm going crazy :)