Cannot bind argument to parameter 'Identity' because it is null

When attempting to install Exchange 2010 SP3 Service Pack on an Exchange 2010 SP1 Server I received the following on the Mailbox Server Role.

Error:
The following error was generated when "$error.Clear();
          if ($RoleCreatePublicFolderDatabase)
          {
            $publicDB = get-PublicFolderDatabase -Server:$RoleFqdnOrName -ErrorAction SilentlyContinue;
            $DB = get-MailboxDatabase -Server:$RoleFqdnOrName -ErrorAction SilentlyContinue;
            if ($publicDB -and $DB)
            {
                set-mailboxdatabase `
                  -Identity:$DB.Identity `
                  -publicFolderDatabase:$publicDB.Identity `
                  -DomainController $RoleDomainController
            }                 
          }
        " was run: "Cannot bind argument to parameter 'Identity' because it is null.".
Cannot bind argument to parameter 'Identity' because it is null.

If you received this error you most likely also received:

http://clintboessen.blogspot.com.au/2014/10/this-server-role-cant-be-installed.html

This error occurs if the original Exchange 2010 SP1 or SP2 installation did not finish "Finalizing Setup" which is the final stage in the installation process.  Failure means important registry keys are not set correctly.  In my case the Finalizing Setup did not complete because of the following error:

 

http://clintboessen.blogspot.com.au/2014/10/couldnt-resolve-user-or-group.html

 

This error is generated if the MailboxRole is missing a ConfiguredVersion string value under the following registry key:

 

HKLM\SOFTWARE\Microsoft\ExchangeServer\v14\MailboxRole

 

As you see in the following screenshot the ConfiguredVersion string value is missing:

 

 

Simply create the string value called ConfiguredVersion and give it the same value as UnpackedVersion as shown in the following screenshot:

 

 

After this I deleted the Exchange 2010 SP3 installation watermark (both the “Action” and “Watermark” entries in the registry) and re-ran setup.  Google for this, lots of information already available on the Internet