Checkboxes not showing in html using symfony 4

I'm trying to show checkboxes in a form using symfony 4. I used the same information found on the symfony 4 documentaion Even though they are taken into account when clicking on the label (saved in the DTB) they don't render on the html.

Here's an example of one of the options of the form using a checkbox:

->add('accessibility', CheckboxType::class, [ 'label' => 'Accéssibilité', 'required' => false, ])

however here is the rendering on my page : No checkbox

Let me know if you need any other information, thanks for the help