Silverstripe 3 form not executed

Questions
1

Silverstripe Version: 3.6

Question:

I have problem with submiting form. When i submit form method was not executed in all page types.
I test code from documentation with HelloWorld and again doHelloWorld not executed.
I waste 2 days on this problem and realy dont know what can be problem and whay method was not executed on submit button.

Here is my controller:

This code is form: https://docs.silverstripe.org/en/3/developer_guides/forms/introduction/

class ContactPage_Controller extends Page_Controller
{
    private static $allowed_actions = array(
        'HelloForm'
    );

    public function init()
    {
        parent::init(); // TODO: Change the autogenerated stub
    }

    public function HelloForm() {
        $fields = new FieldList(
            TextField::create('Name', 'Your Name')
        );

        $actions = new FieldList(
            FormAction::create("doSayHello")->setTitle("Say hello")
        );

        $required = new RequiredFields('Name');

        $form = new Form($this, 'HelloForm', $fields, $actions, $required);

        return $form;
    }

    public function doSayHello($data, Form $form) {
        return $this->redirect("/");
    }
}

This is my code also not working:

Also i try module Userforms and that also not working.
Before 5 days i create one form on HomePage and worked good, but when i create new Page type and create new contact form all start bugging. Anyone can help me and explain me what is happening here. I’m starting to crazy