How to different repadmin /showrepl * /csv >showrepl.csv and repadmin /showrepl * /csv

I running script on domain controller 

repadmin /showrepl * /csv >showrepl.csv   = export to CSV file  can see all the  DC in forrest.

and  repadmin /showrepl * /csv

Why when run script repadmin /showrepl * /csv =  Report cannot get information from all DC in forrest.  But can show some DC in forrest.

#Check the Replication with Repadmin
$workfile = c:\rep\repadmin.exe /showrepl * /csv



$results = ConvertFrom-Csv -InputObject $workfile | where {$_.'Number of Failures' -ge 1}
$strOutFile = "c:\rep\Check-Replication.htm"


#Here you set the tolerance level for the report
#$results = $workfile | where {$_.'Number of Failures' -gt 1 }

if ($results -ne $null ) {
$results = $results | select "Source DC", "Destination DC", "Naming Context" , "Last Failure Time", "Last Success Time" | ConvertTo-Html
} else {
$results = "There were no Replication Errors"
}
Send-MailMessage -From $from -To $to -Subject "Daily Forest Replication Status" -SmtpServer "mailserver" -BodyAsHtml ($results | Out-String)

$filedate = get-date
$filedate = $filedate.ToString()

$results = "" + $filedate + "" + $results + ""
$results | Out-File $strOutFile