Advantage Database Server Management API AdsMgKillUser not working?

Question

I wrote a utility in Delphi 5.0 to disconnect crashed connections in ADS v6.2 using AdsMgKillUser that worked well for many years on a customer's server. Customer recently upgraded to ADS v9.1 and 2008 Server: the old utility stopped working. Updated program to Delphi 7, ADS v9.1 TDataSet and ACE. Using code copied almost verbatim from the AdsMgKillUser help topic, testing against an ADS 10.1 server, code fails to disconnect user, (but I get an AE_SUCCESS return code when calling AdsMgKillUser). ARC32 v9.1 works fine on the same test to disconnect an ADS 10.i user.

Code Snippet:

// program resides on same server as ADS
ulRetVal := ACE.AdsMgConnect( PAnsiChar(appdir), nil, nil, @hMgmtHandle );

if ( ulRetVal <> AE_SUCCESS ) then
begin
    Application.MessageBox( 'Could not connect to server.', 'Connection Error', ID_OK );
    exit;
end;
// strUserConn assigned connection name in format domain\username e.g. "MYSERVER\Fred"
ulRetVal := ACE.AdsMgKillUser( hMgmtHandle, PAnsiChar(strUserOrConn), 0);
if ( ulRetVal <> AE_SUCCESS ) 
then Application.MessageBox( 'User not disconnected.','Error', ID_OK )
else Application.MessageBox( 'User disconnected OK','Information', ID_OK );

What am I doing wrong?