Error "Service Unavailable HTTP Error 503. The service is unavailable" on the second ADFS server

hi all,

Im deploying ADFS for SSO for Office 365 , i installed and configured the first ADFS successfully with no issues , also installed and configured the second ADFS with no issues but when i test if it's working or not using the below URL

https://localhost/FederationMetadata/2007-06/FederationMetadata.xml 

i got this error "Service Unavailable HTTP Error 503. The service is unavailable" 

Thanks

Tarek Khairy