WordPress plugin choices web page not saving choices, no errors

My plugin’s choices web page has two string choices: username and access_key. After I enter my username and click on “Save Adjustments”, the web page reloads, however the username will not be current within the possibility subject.

If I add var_dump($_POST); to my possibility’s web page output, I see array(0) { } on the subsequent web page load after attempting to avoid wasting choices.

Right here is my plugin’s choices.php file:

if (is_admin()) {
    add_action( 'admin_menu', 'example_portfolio_options_page' );
}

operate example_portfolio_options_page() {

    //create new top-level menu
    add_menu_page('Instance Portfolio Settings', 'Instance', 'administrator', __FILE__, 'example_portfolio_options_page_form', 'dashicons-admin-generic');

    //name register settings operate
    add_action( 'admin_init', 'example_portfolio_settings' );

    if ( ! isset( $_POST['example_portfolio_options_update_nonce'] ) ) {
        return;
    }
    
    if ( ! wp_verify_nonce( $_POST['example_portfolio_options_update_nonce'], 'example_portfolio_options_update' ) ) {
        return;
    }
    
    // Replace the 'username' possibility with the brand new worth entered by the person
    if ( isset( $_POST['username'] ) ) {
        update_option( 'example_portfolio_username', sanitize_text_field($_POST['username']) );
    }
    
    // Replace the 'username' possibility with the brand new worth entered by the person
    if ( isset( $_POST['access_key'] ) ) {
        update_option( 'example_portfolio_access_key', sanitize_text_field($_POST['access_key']) );
    }
}

operate example_portfolio_settings() {
    add_options_page(
        'Instance Writer Portfolio',
        'Instance Writer Portfolio',
        'manage_options',
        'example_portfolio',
        'example_portfolio_options_page'
    );

    register_setting( 'example_portfolio_options', 'example_portfolio_options', 'example_portfolio_options_validate' );

    add_settings_section(
        'example_portfolio_settings_section',
        __( 'Instance Writer Portfolio Settings', 'example_portfolio' ),
        'example_portfolio_settings_section_callback',
        'example_portfolio_options'
    );
    
    add_settings_field(
        'example_portfolio_username',
        __( 'Instance.com Username', 'example_portfolio' ),
        'example_portfolio_username_callback',
        'example_portfolio_options',
        'example_portfolio_settings_section'
    );
    
    add_settings_field(
        'example_portfolio_access_key',
        __( 'Instance API Entry Key', 'my_plugin' ),
        'example_portfolio_access_key_callback',
        'example_portfolio_options',
        'example_portfolio_settings_section'
    );

    operate example_portfolio_settings_section_callback() {
        echo '<p>Enter your Instance username and entry key under:</p>';
    }

    operate example_portfolio_username_callback() {
        $choices = get_option( 'example_portfolio_options' ) ?: array();
        echo '<enter sort="textual content" id="example_portfolio_options_username" title="example_portfolio_username" worth="' . $choices['username'] . '" />';
    }
    
    operate example_portfolio_access_key_callback() {
        $choices = get_option( 'example_portfolio_options' ) ?: array();
        echo '<enter sort="textual content" id="example_portfolio_options_access_key" title="example_portfolio_access_key" worth="' . $choices['access_key'] . '" />';
    }

    add_option( 'example_portfolio_username', '' );
    add_option( 'example_portfolio_access_key', '' );

}

operate example_portfolio_options_page_form() {
    if ( ! current_user_can( 'manage_options' ) ) {
        return;
    }
    var_dump($_POST);
    ?>
    <div class="wrap">
        <kind motion="choices.php" technique="put up">
            <?php
                settings_fields( 'example_portfolio_options' );
                do_settings_sections( 'example_portfolio_options' );
                submit_button();
                wp_nonce_field( 'example_portfolio_options_update', 'example_portfolio_options_update_nonce' );
            ?>
        </kind>
    </div>
    <?php
}

Is my <kind motion="choices.php" technique="put up"> coded accurately?

Assist appreciated.