PhpSpreadsheet not Found

I have a controller that can import data from an excel file using PhpSpreadsheet and I installed it with composer.
It works when I use it on my local computer
but after I upload it to the server Debian, the error showed
Class 'PhpOffice\PhpSpreadsheet\Reader\Xls' not found

this is my Controller code

use PhpOffice\PhpSpreadsheet\Helper\Sample;
use PhpOffice\PhpSpreadsheet\IOFactory;
use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\Writer\Xlsx;

    public function import()

        $group_id = $this->request->getData()['group_id'];
        $files = $this->request->getUploadedFiles();
        $tmpFilePath = $files['import']->getStream()->getMetadata('uri');        

        $myname = $this->request->getData()['import']->getClientFileName();
        $myext = substr(strchr($myname, "."), 1);
        if ($myext == 'xls') {
            $reader = new \PhpOffice\PhpSpreadsheet\Reader\Xls();
        }else if($myext == 'xlsx'){
            $reader = new \PhpOffice\PhpSpreadsheet\Reader\Xlsx();
        $spreadsheet = $reader->load($tmpFilePath);
        $sheet = $spreadsheet->getActiveSheet()->toArray();
        foreach ($sheet as $key => $excel){
            if ($key == 0) {
            $data = [
                'nis' => $excel[1],
                'name' => $excel[2],
                'password' => $excel[1],
                'group_id' => $group_id,
            $student = $this->Students->newEmptyEntity();
            $student = $this->Students->patchEntity($student, $data);
            if ($excel[1] != null AND $excel[2] != null) {
                if ($this->Students->save($student)) {
                    $this->Flash->success(__('The student has been saved.'));
                $this->Flash->error(__('The student could not be saved. Please, try again.'));
        return $this->redirect(['action' => 'detail', $group_id]);

Please I need your help

manually uploading the vendor directory doesn’t always work.

Either try dumping the autoloader via

composer dump-autoload

or try re-installing the composer modules on your live server via

rm -rf vendor
composer install

Thank you, It work
I try to install composer in my server and install the spreadsheet