AWS SNS push notification

While create platform application

when i tried to create application and push notification platform select GCM then add API key i got this.

any body has idea.

Invalid parameter: Attributes Reason: Platform credentials are invalid (Service: AmazonSNS; Status Code: 400; Error Code: InvalidParameter; Request ID: 44a04d15-c58b-5bf8-859e-0311947aac6c)