why button action cannot add attributes

this is my code

        protected function getActions(): array
    {
        return [
            buttonAction::make('UPLOAD')->extraAttributes(['class' => 'button'])
                ->action('kkp')
                ->requiresConfirmation()
                ->modalHeading('UPLOAD FILE')
                ->modalButton('UPLOAD FILE')
                ->form([
                    FileUpload::make('attachment')
                        ->extraAttributes(['class' => 'custom'])
                        ->label('UPLOAD SURAT PENGANTAR')
                        ->required()
                ]),
        ];
    }

why cannot add attributes button action on Fillament Laravel I was try to add FileUpload components and this work after that i try to add attributes on button action but didn't work ??