• Cannot access the vCenter Server Managed Object Browser (MOB) at https://vCenterFQDN/mob/
• The browser reports the error:
  
  503 Service Unavailable
  

Note: The VMware VirtualCenter Server service and other related services are up and running.

• Replacing the SSL certificates of the vCenter Server using the SSL Automation Tool 1.0.x or 5.5.x fails with the error:

[Tue 01/28/2014 - 11:07:13.83]: Validating the input parameters...
STATE : 4 RUNNING
HTTPError: Unable to open or read page.
HTTP Error 503: Service Unavailable
[Tue 01/28/2014 - 11:07:14.77]: "Cannot log in to vCenter."
[Tue 01/28/2014 - 11:07:14.78]: The vCenter certificate update failed.

To resolve this issue:

1. In vCenter Server, open the vpxd.cfg config file using a text editor.
   
   Note: By default, the vpxd.cfg file is located at %ALLUSERSPROFILE%\Application Data\VMware\VMware VirtualCenter. In Windows Server 2008, the vpxd.cfg file is, by default, located at C:\ProgramData\VMware\VMware VirtualCenter.
   
   
2. Locate the <enableDebugBrowse> entry within the file.
3. Either remove the entry or change the value from false to true.
   
   For example:
   
   <vpxd>
   ...
   ...
   <enableDebugBrowse>false</enableDebugBrowse>
   ...
   ...
   </vpxd>
   
   
4. Restart the vCenter Server services for the changes to take effect. For more information, see Stopping, starting, or restarting vCenter services (1003895).