validation privacy checkbox

hello,
i have a problem with validation of privacy policy on custom form

this is my custom form:

<div class="tnp tnp-subscription">
<div class="row">
<div class="col-lg-7">
<div class="footer-news-title">Ricevi il <strong>10%</strong> DI SCONTO SUL PRIMO ORDINE!</div>
<div class="footer-news-desc"><p>Iscriviti alla nostra newsletter per ricevere aggiornamenti sui nuovi prodotti, offerte speciali e altre informazioni sul Il Crogiuolo.</p>
</div>
</div>
<div class="col-lg-4 offset-lg-1">
<form method="post" action="https://ilcrogiuolo.it/en/?na=s" onsubmit="return newsletter_check(this)">

<input type="hidden" name="nlang" value="it">
<div class="tnp-field tnp-field-email"><input class="tnp-email sib-email-area" type="email" name="ne" required  placeholder="Inserisci la tua email qui *"></div>
<input type="checkbox" name="ny" id='footer-privacy' ><label for='footer-privacy' class='footer-privacy'><span>Dichiaro di aver letto l'<a href="/it/cookie-policy/">informativa sulla privacy</a> e acconsento al trattamento dei miei dati.</span></label>

<div class="tnp-field tnp-field-button"><input class="tnp-submit" type="submit" value="Iscriviti" >
</div>

</form>
</div>
</div>
</div>

if i add a required on checkbox field appears an error:
An invalid form control with name=’ny’ is not focusable.

if i don’t set required on checkbox field the form can be submit without sign checkbox privacy

how i can set required a checkbox?

thank you