Why related state / region selection field does not work?

In laravel 10 / filamentphp 3 app I have 3 related country/state/region fields referencing table :

CREATE TABLE `geo` (
  `id` int unsigned NOT NULL AUTO_INCREMENT,
  `parent_id` int DEFAULT NULL,
  `left` int DEFAULT NULL,
  `right` int DEFAULT NULL,
  `depth` int NOT NULL DEFAULT '0',
  `name` char(60) COLLATE utf8mb4_unicode_ci NOT NULL,
  `alternames` text COLLATE utf8mb4_unicode_ci NOT NULL,
  `country` char(2) COLLATE utf8mb4_unicode_ci NOT NULL,
  `a1code` varchar(25) COLLATE utf8mb4_unicode_ci NOT NULL,
  `level` char(10) COLLATE utf8mb4_unicode_ci NOT NULL,
  `population` bigint NOT NULL,
  `lat` decimal(9,6) NOT NULL,
  `long` decimal(9,6) NOT NULL,
  `timezone` char(30) COLLATE utf8mb4_unicode_ci NOT NULL,

When user selects country, then all states are filled correctly, but the simalar functionality does not work when I need to fill all regions ('region' selection input) by selected state('state_id' selection input) :

              ->schema([
                     Select::make('country')->label('Country')
                         ->prefixIcon(getLocationIcon())
                         ->preload()
                         ->live(onBlur: true)
                         ->options(ProfileHelper::getCountrySelectionItems(false))
/*returned array :

[en] => USA
[es] => Spain
[ua] => Ukraine
*/
                         ->default(ProfileHelper::getDefaultCountry())
                         ->helperText('Select one countries which are used in the app '),

                     /* BY SELECTING state OF country above list of regions in select below is autofilled */
                     Select::make('state_id')->label('State 987')  // THIS SELECTION IS FILLED CORRECTLY
                         ->options(function (callable $get) {
                             if (empty($get('country'))) {    // THAT IS VALID COUNTRY
                                 return [];
                             }
                             return Geo::getByCountry($get('country'))->getByLevel('ADM1') ->orderBy('name')->pluck('name', 'id');
                         })
                         ->helperText('Select state of the country selected above'),

                     Select::make('region')->label('region')
                         ->options(function (callable $get) {
                             \Log::info(varDump($get('state_id'), ' -145 $get(state_id)::')); // BUT THIS VALUE IS ALWAYS NULL

                             if (empty($get('state_id'))) {
                                 return [];
                             }

                             // SO THE SELEXCTION BELOW IS NOT AUTOFILLED!
                             return Geo::getByCountry($get('country'))->getParentId($get('state_id'))->getByLevel('ADM2')->orderBy('name')->get();
                         })
                         ->helperText('Select region of the state selected above'),

                     TextInput::make('town')
                         ->maxLength(100),
                     TextInput::make('postal_code')
                         ->maxLength(6),
                 ])

What can be wrong in my code ?