Your Operation was forbidden issue in Firebase Console

To get Debug certificate run this command C:\Program Files\Java\jdk1.8.0_131\bin key tool comes with the Java SDK.

keytool -list -v -keystore C:\Users\DELL\.android\debug.keystore -alias androiddebugkey -storepass android -keypass android

Finally I Have solved issue my self,

Firebase internally stores each package name with associated SHA-1 Key. So When we are using same package name & SHA-1 in firebase, it will not allow to user it and produce the same error mentioned in the question. To solve we need to either change package name or need to user another keystore's SHA-1 key.

You may have/had an app in any firebase project with same package name/bundle id and SHA1 fingerprint. I had tried to delete the certain app from the project that I created earlier. But it won't help me even after 24 hours of app delete operation. (I believe that it will take some time for update the app details in the firebase projects config)

So I had tried to delete the entire firebase project that I created earlier and tried to create the new app with same details in the new firebase project.

It Works... (In my case I was aware of two firebase projects that have the apps with same details)