If you loaded the helpers correctly, check that you correctly include the stylesheets and scripts from Bootstrap, since the helpers do not include them automatically.
faIcon and glIcon methods gone?The faIcon and glIcon have been dropped in 3.1.0, alongside with the useFontAwesone option. If you
want to use a custom set of icons, you can customize the icon template:
$this->Html->templates([
'icon' => '<i class="fa fa-{{type}}"></i>'
]);
The easy icon features relies on the Bootstrap.Html helper, so it only works if the Html helper
associated to your view is Bootstrap.Html:
public $helpers = [
'Html' => [
'className' => 'Bootstrap.Html'
]
];