Error on accessing URL

Hi,

 I am getting the following error in browser ,when i try to access the below URL :
    
 https://projectsapi.zoho.com/restapi/portals/

 Error

 ------

 <error>

  <code>
  6500
  </code>
 

  <message>
  General Error
  </message>
 

 </error>

 Anyone, Please help on this