Convert-To-HTML works but ConvertTo-HTML -fragment doesn't

Here's my scenario; I have a script that produces an HTML report and am trying to incorporate it into an larger HTML report using the -fragment switch. Why doesn't it work?
Code that works;

Function OPorts {
      $process = "Open Ports"
      $reportfile = $strfolderpath + "Open Ports.html"
            $strnmap = nmap -sW -sV $strcomputer
            $nmap = @()
                  Foreach ($Line in $strnmap) {
                  $Object = New-Object -TypeName PSObject
                  Add-Member -InputObject $Object -Type NoteProperty -Name Log -Value $Line
                  $nmap += $Object
                  }
            $nmap | ConvertTo-HTML -head $pstyle -body "<H1>Open Ports</H1>" | Out-File $reportfile       
      }

code that doesn't work;

$nmap = @()
      $TotalPorts = @()

            foreach ($computer in $strComputer) {
                  $strnmap = nmap -sW -sV $computer
                        Foreach ($Line in $strnmap) {
                              $Object = New-Object -TypeName PSObject
                              Add-Member -InputObject $Object -Type NoteProperty -Name Log -Value $Line
                  $nmap += $Object
                  }
            $nmap | ConvertTo-HTML -fragment
            $TotalPorts += $nmap
            }
#      $TotalPorts | ConvertTo-HTML -fragment

On the "fragment" code I'll get a printout on the console of the HTML with the correct information, but it won't appear in the report. I have several other items in this HTML report that work fine.

BTW; this is the code that inserts it into the report.

<h3>Open Ports</h3>
      <p>The following is a summary of the Open Ports</p>
      <table class="normal">
      $TotalPorts ****I've also used $nmap here ******
      </table>

I'm on Version 3 of powershell.
Thanks in advance.