Return value of Spatie\Newsletter\NewsletterList::getId() must be of the type string, null returned

[farshadff]

on laravel 8 i do it like below :

 public function store(Request $request)
    {
        Newsletter::subscribe('rincewind@discworld.com');

        return redirect('newsletter')->with('failure', 'Sorry! You have already subscribed ');

    }

but i get this error :

and one other question is that do i need the Newsletter model ??

[putrafajarh]

you need to fill env MAILCHIMP_LIST_ID https://mailchimp.com/help/find-audience-id/