Problems with checkbox when trying to register

Hello,

The plug in that we are using is Tutor LMS PRO by Thenum, it generates our page for registartion,
hance the registration form is automatically created by thenum. I can add the checkbox for
automatical supscritpion to the emails, from the menu of mailpoet ( Settings -> ‘Subscribe in registration form’ checkbox ),
however when I add it and users try to register, a fatal error appears, and users are not registarted nor subscribed.
Is there a way,  that I can add custom code in a Code Snippets plug in?
I have added an additional checkbox for the privacy policy with this code :
function extracheckbox() { ?>
    <div class=”tutor-form-row”>
<div class=”tutor-form-col-12″>

<div class=”tacbox”>
  <input id=”checkbox” type=”checkbox” required/>
  <label for=”checkbox”> Съгласявам се с  <a href=”https://eacademiabg.com/%d0%bf%d0%be%d0%bb%d0%b8%d1%82%d0%b8%d0%ba%d0%b0-%d0%b7%d0%b0-%d0%bf%d0%be%d0%b2%d0%b5%d1%80%d0%b8%d1%82%d0%b5%d0%bb%d0%bd%d0%be%d1%81%d1%82/“>Правила и условия</a>.</label>
</div>

</div>
</div>
<?php }
add_action( ‘tutor_student_reg_form_end’, ‘extracheckbox’, 999 );