Hi, i had the same issue with you and i solved it. Hope not too late to help you.
First, you need to check your gmail by go into "My Account" > Sign-in & security > then enable Apps connected to your account
Second, make sure your send to email is added to email configuration with the correct password that login into your gmail account
Third, make sure that your template key and value is match ( NSMutableDictionary *otherMetaHeaders = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"test",@"test", nil];//Which you are created from AppHQ.)