i have the same problem, i've tried to change permission on the Security section of the main and sub folders.
i changed temp_dir =>
to many locations as storage_path('/temp')
// public_path('temp')
// base_path('temp')
but notthing new , always getting same error.
Temporary files directory "C:\inetpub\wwwroot\laravel\../temp//mpdf" is not writable
i deployed my project laravel on windows server
I found a solution.
i added tempdir
path as parameter in loadview function
$pdf = PDF::loadView('pdf', $data, [], ['tempDir' => storage_path('tempdir') ])->save($pdfFilePath);
$pdf->stream('nicesnippets.pdf');