Error: options page not found when I try to save the changes made in my settings page

I'm developing a plugin... everything was fine but suddenly when I try to save the plugin settings... I found with the error that says the page options not found..

I was looking for some answer but not one fix my error... Following some code that makes the settings page and save the options in the database:

admin.php

?php
/**
 *
 * This file contains the necesary functions to display the admin area of the plugin
 *
 * @author  Ezequiel Cattaneo [email protected]
 *
 * @link    https://webstower.com.ar/wtdomcheck
 * @since   1.0.0
 *
 **/

require_once WTDOMCHECK_PLUGIN_DIR.'admin/class/class-admin.php';

$wtdomadmin = '';

//All the magic is done here!
if ( class_exists('admin') ) {
    
    $wtdomadmin = new admin();
    $wtdomadmin-WTRegister();

}
?

class_admin.php

function __construct() 
    {

        //Instantiate the API that will construct our admin pages
        $this-settings = new ApiWpadmin();

        //Array of pages to create
        $this-pages = [
            [
                'page_title' = 'My plugin settings page', 
                'menu_title' = 'Settings page', 
                'capability' = 'manage_options', 
                'menu_slug'  = 'wtdomaincheck', 
                'callback'   = array($this, 'WTLoadSettingTemplate'), 
                'icon_url'   = 'dashicons-admin-generic', 
                'position'   = 117
            ]
        ];
        
    
        //Register the settings in the database
        add_action('admin_init', array($this, 'WTSaveSettings'));
    }



    //
    // PARAM
    // Register all the actions  filters for wp-admin
    //
    public function WTRegister() 
    {

        $this-settings-
            WTAddPages( $this-pages ) -
            WTWithSubPage( 'Dashboard' ) -
            WTAddSubPages( $this-subpages ) -
            WTRegister();

    }


    //
    // PARAM
    // Register the settings values in the database
    //
    public function WTSaveSettings()
    {
            $wt_options = array (
                'display-on-free'       = $_POST['display-on-free'],
                'display-on-registered' = $_POST['display-on-registered'],
                'display-on-invalid'    = $_POST['display-on-invalid'],
                'before-whois-output'   = $_POST['before-whois-output'],
                'after-whois-output'    = $_POST['after-whois-output'],
                'callurl'               = $_POST['callurl'],
                'varname'               = $_POST['varname'],
                'resp-free-domain'      = $_POST['resp-free-domain'],
                'resp-registered-domain'= $_POST['resp-registered-domain'],
                'resp-invalid-domain'   = $_POST['resp-invalid-domain'],
                'custom-css'            = $_POST['custom-css'],
                'license-key'           = $_POST['license-key'],
                'style-box-bgcolor'     = $_POST['style-box-bgcolor'],
                'style-www-color'       = $_POST['style-www-color'],
                'style-button-color'    = $_POST['style-button-color'],
                'style-button-bgcolor'  = $_POST['style-button-bgcolor'],
                'style-result-color'    = $_POST['style-result-color'],
                'style-result-bgcolor'  = $_POST['style-result-bgcolor']
            );

            if (isset($_POST['enable-multiple-search'])) 
                $wt_options[] = array('enable-multiple-search' = $_POST['enable-multiple-search'] );

            if (isset($_POST['show-www'])) 
                $wt_options[] = array('show-www' = $_POST['show-www'] );

            if (isset($_POST['show-whois-output'])) 
                $wt_options[] = array('show-whois-output' = $_POST['show-whois-output'] );

            update_option( 'wtdomaincheck', $wt_options );
    }



    //
    // PARAM
    // Loads the template that shows the settings page
    //
    public function WTLoadSettingTemplate()
    {
        
        require_once WTDOMCHECK_PLUGIN_DIR.'admin/html/settings.php';
    }

?

settings.php

form method=post action=options.php

        ?php settings_fields( 'wtdomaincheck' ); ?

        div class=row border
            
            div class=col-3 border-right pt-3 pb-3
                div id=pillTabs class=nav flex-column nav-pills id=v-pills-tab role=tablist aria-orientation=vertical
                    ?php
                    //Build Pill Sections
                    echo $wtdomadmin-WTBuildPillTabs($sections);
                    ?
                /div
            /div

            div class=col-9 pt-3
                div class=tab-content id=v-pills-tabContent
                    ?php
                    //Build Pill Sections
                    echo $wtdomadmin-WTBuildPillPanes($sections);
                    ?
                /div
            /div
        
        /div
        
        div class='form-group row mx-auto mt-3'
            div class=col-lg-12 pr-0
                input type=submit class=btn btn-primary float-right value=?php _e('Save Changes') ? /
            /div
        /div

    /form

When I install the plugin, the options record is created in the wp_options table. The settings page is displayed.. but when I try to save the changes... is where the options page not found comes to the screen...

Any help will be appreciated.