Following CSV file script are not working properly in Laravel 6 - mysql

Question

I used following script in my rout file.
Route::get('/tasks', 'appointmentController#exportCsv')
I used the following Js script Html Clickable button in blade template
<script>
function exportTasks(_this) {
let _url = $(_this).data('href');
window.location.href = _url;
}
</script>
<span data-href="./tasks" id="export" class="btn btn-success btn-sm" onclick="exportTasks(event.target);">Export Client Email</span>
I used the following script in my controller. I cant find where is the script problem. CSV file are not download include with the data.
public function exportCsv(Request $request)
{
$fileName = 'tasks.csv';
$tasks = Clientinformation::all();
$headers = array(
"Content-type" => "text/csv",
"Content-Disposition" => "attachment; filename=$fileName",
"Pragma" => "no-cache",
"Cache-Control" => "must-revalidate, post-check=0, pre-check=0",
"Expires" => "0"
);
$columns = array('customerName', 'email', 'cell1', 'cell2', 'landNumber');
$callback = function() use($tasks, $columns) {
$file = fopen('php://output', 'w');
fputcsv($file, $columns);
foreach ($tasks as $task) {
$row['customerName'] = $task->customerName;
$row['email'] = $task->assign->email;
$row['cell1'] = $task->cell1;
$row['cell2'] = $task->cell2;
$row['landNumber'] = $task->landNumber;
fputcsv($file, array($row['customerName'], $row['email'], $row['cell1'], $row['cell2'], $row['cell2'], $row['landNumber'] ));
}
fclose($file);
};
return response()->stream($callback, 200, $headers);
}