Form in custom page validation not working

class Checkout extends Page implements HasForms
{
    use InteractsWithForms;
....

    protected static string $view = 'filament.admin.resources.invoice-resource.pages.checkout';

    public ?array $data = [];

 public function form(Form $form): Form
    {
        return $form
            ->statePath('data')
            ->schema([
                Forms\Components\Section::make('Payment Information')
                    ->schema([
                        Forms\Components\Select::make('paymentMethod')
                            ->label('Payment Method')
                            ->options($this->getPaymentMethods())
                            ->live()
                            ->required(),

                        Forms\Components\Section::make(fn($get) => 'Payment with ' . $get('paymentMethod'))
                            ->visible(fn($get) => $get('paymentMethod') !== null)
                            ->schema(fn($get) => is_null($get('paymentMethod')) ? [] : $this->factory->resolve($get('paymentMethod'))->form()),
                    ]),
            ]);
    }