In the release of MET/TEAM version 2.3.0, there is a known issue when updating the Customer Portal that has been installed on a server that is different from the main MET/TEAM server machine.
At the end of the update process, you will receive an error message like this one:
To resolve this issue, open the "Web.config" file using notepad or other text editor program for your main MET/TEAM installation (located on the server at C:\inetpub\wwwroot\METTEAM by default) and find the following line:
<add key="SerialNumber" value="00000000-0000-0000-0000-000000000000" />
In place of zeros, your file will contain a GUID for the Serial Number of your server.
Navigate to the same file on the Customer Portal server (located on the server at "C:\inetpub\wwwroot\CustomerPortal\web.config" by default) and you will see that the value on this line is empty.
<add key="SerialNumber" value="" />
Copy the value from the main MET/TEAM server and paste it into the same line in the "Web.config" file on your Customer Portal server. Save the file and close both files.
This will allow Customer Portal to run properly.