Laravel (5.8) observer deleted is not working

I am using Laravel (5.8) and I need to delete a record from table A and then also table B. So I tried Observers, but it never fired the observer's deleted method.

I already used other methods like updating or updated, so I don't know why the deleted method is not firing.
I don't use soft delete, because I didn't make this database schema and I don't have authorities to modify that. But based on what I read from the document, it doesn't matter..right?

Here are my code.

• Pay Controller.php

public function delete(Request $request, $idx){
    $payData = PaymentData::where('idx', $idx)->delete();
    return response()->json(['status' => true]);
}

• PayObserver.php

public function deleted(PaymentData $paymentData)
{
        if ($paymentData->pay_type == "PA") {
            $app = AppData::where('oid', $paymentData->oid)->first();

            if (!empty($app)) {
                $app->delete();
            }
        }
}

• AppServiceProvider.php

public function boot()
{
    \App\Models\PaymentData::observe(\App\Observers\PayObserver::class);
}

I also tried to add the observe statement to boot method in EventServiceProvider.php, but it wasn't working either.
I read the official document but couldn't find any clues..what did I miss?

via Chebli Mohamed