Powershell script to write SQL results to xlsx - Excel sheet is blank even though the query returns records - sql-server

Question

We're writing the following Powershell script to run a simple SELECT statement against our SQL Server database and dump the results into an Excel file. The query returns 4 records but the resulting Excel file is blank. I can't determine why this would be.
This is what I have so far:
$FileName = "C:\Users\Me\Documents\TestFile.xlsx";
$ConnectionString = "Our DB connection string"
$SqlQuery = #"
SELECT Id
FROM dbo.Orders
WHERE OrderExpiry IS NULL
AND ReturnPeriod IS NULL
AND Returned IS NULL
"#;
#Connect to SQL Server using non-SMO class System.Data
$SqlConnection = New-Object System.Data.SqlClient.SqlConnection;
$SqlConnection.ConnectionString = $ConnectionString;
$SqlCmd = New-Object System.Data.SqlClient.SqlCommand;
$SqlCmd.CommandText = $SqlQuery;
$SqlCmd.Connection = $SqlConnection;
$SqlCmd.CommandTimeout = 60
## – Extract and build the SQL data object ‘$DataSetTable’:
$SqlAdapter = New-Object System.Data.SqlClient.SqlDataAdapter;
$SqlAdapter.SelectCommand = $SqlCmd;
$DataSet = New-Object System.Data.DataSet;
$SqlAdapter.Fill($DataSet);
$DataSetTable = $DataSet.Tables["Table"];
## – Create an Excel Application instance:
$xlsObj = New-Object -ComObject Excel.Application;
## – Create new Workbook and Sheet (Visible = 1 / 0 not visible)
$xlsObj.Visible = 0;
$xlsWb = $xlsobj.Workbooks.Add();
$xlsSh = $xlsWb.Worksheets.item(1);
## – Build the Excel column heading:
[Array] $getColumnNames = $DataSetTable.Columns | Select ColumnName;
## – Build column header:
[Int] $RowHeader = 1;
foreach ($ColH in $getColumnNames)
{
$xlsSh.Cells.item(1, $RowHeader).font.bold = $true;
$xlsSh.Cells.item(1, $RowHeader) = $ColH.ColumnName;
$RowHeader++;
};
## – Adding the data start in row 2 column 1:
[Int] $rowData = 2;
[Int] $colData = 1;
foreach ($rec in $DataSetTable.Rows)
{
foreach ($Coln in $getColumnNames)
{
## – Next line convert cell to be text only:
$xlsSh.Cells.NumberFormat = "#";
## – Populating columns:
$xlsSh.Cells.Item($rowData, $colData) = `
$rec.$($Coln.ColumnName).ToString();
$ColData++;
};
$rowData++; $ColData = 1;
};
## – Adjusting columns in the Excel sheet:
$xlsRng = $xlsSH.usedRange;
$xlsRng.EntireColumn.AutoFit();
## – Saving Excel file – if the file exist do delete then save
$xlsFile = $FileName;
if (Test-Path $xlsFile)
{
Remove-Item $xlsFile
$xlsObj.ActiveWorkbook.SaveAs($xlsFile);
}
else
{
$xlsObj.ActiveWorkbook.SaveAs($xlsFile);
};
## Quit Excel and Terminate Excel Application process:
$xlsObj.Quit(); (Get-Process Excel*) | foreach ($_) { $_.kill() };
$SqlConnection.Close()
$Attachment = $xlsFile
Upon executing the script, once the query runs successfully, the script outputs 4 (which is the number of records this query returns) and also outputs True, and the Excel file gets successfully created. But it's blank. Any ideas why I'm getting blank output?