Exception: Invalid Credentials for Cloud SQL #955

javax.servlet.ServletException: Unable to connect to Cloud SQL
	at com.example.appengine.cloudsql.CloudSqlServlet.init(CloudSqlServlet.java:116)
	..........
	... 65 more
Caused by: java.lang.RuntimeException: Unable to retrieve information about Cloud SQL instance [shamalk:us-central1:db-1]
	at com.google.cloud.sql.core.SslSocketFactory.obtainInstanceMetadata(SslSocketFactory.java:411)
	.............
	... 78 more
Caused by: com.google.api.client.googleapis.json.GoogleJsonResponseException: 401 Unauthorized
{
  "code" : 401,
  "errors" : [ {
    "domain" : "global",
    "location" : "Authorization",
    "locationType" : "header",
    "message" : "Invalid Credentials",
    "reason" : "authError"
  } ],
  "message" : "Invalid Credentials"
}
	at com.google.api.client.googleapis.json.GoogleJsonResponseException.from(GoogleJsonResponseException.java:146)
	..............
	... 86 more