Horizontally centering a div within a div – WordPress

I’m working on including a shortcode on the footer of my WordPress website so that users may sign up to my newsletter.

I managed to include the shortcode itself on the footer, although I can’t get it horizontally centered, it seems stuck on the left side. As you can see, I’ve created a class with two IDs inside of it, the first one with some written text and the second one with the form. The written text is centered, but I can’t find the right way to center the form.

I tried different potential solutions, such as this, this and this, but none of them got it properly centered, it always stays off. I’m sure the solution must be simple, I just can’t see it.

Non working code (solution is shown below):

.tnp-subscription-minimal input[type=submit] {
  background-color: #224b37!important;
  color: #ffffff;
  font: Poppins, sans-serif;
  font-weight: bold;
  margin: 0 auto;
  border: none;
  padding: 0 30px;
  border-radius: 5px;
  letter-spacing: 1px;
  font-size: 14px;
  box-shadow: 0px 8px 15px rgba(0, 0, 0, 0.1);
  cursor: pointer;
  box-sizing: border-box;
  margin-left: 2px;
  transition: all 0.23s ease-in-out 0s;
}

.tnp-subscription-minimal input[type=email] {
  font-family: Poppins, sans-serif;
  border: none;
  padding: 15px;
  width: 50%;
  font-size: 14px;
  margin-right: 5px;
  -webkit-border-radius: 0px;
  -moz-border-radius: 0px;
  border-radius: 5px;
  color: #343434;
  background-color: #fff;
  box-sizing: border-box;
}

#inscripcion {
  font-size: 16px;
  font: Poppins, sans-serif;
  font-weight: 600;
  margin: 0 0 20px;
  color: #000000;
  text-align: center;
}

<div class=“newsletter-wrapper” style="position: sticky; background-color:#c2cdc8; padding:60px 30px 60px 30px; width: 100%;">
  <div id="inscripcion" style="absolute: sticky; left: 50%; top: 50%; z-index: 9999">¿Quieres recibir todos mis posts? ⦙ <br> Do you want to receive my posts?</div>
  <div id="formulario-newsletter"  style="absolute: sticky; left: 50%; top: 50%;">
    <form calss="tnp-subscription-minimal">
      <input type="email" /> <button type="submit">OK!</button>
    </form>
  </div>
</div>

I deliberately left the previous, non-working code in case it helps someone in a similar situation, this is how it ended up looking (and working properly):

.tnp-subscription-minimal input[type=submit] {
  background-color: #224b37!important;
  color: #ffffff;
  font: Poppins, sans-serif;
  font-weight: bold;
  margin: 0 auto;
    width: 16%;
  border: none;
  padding: 0 0px;
  border-radius: 5px;
  letter-spacing: 1px;
  font-size: 14px;
  box-shadow: 0px 8px 15px rgba(0, 0, 0, 0.1);
  cursor: pointer;
  box-sizing: border-box;
  margin-left: 2px;
  transition: all 0.23s ease-in-out 0s;
}

.tnp-subscription-minimal input[type=email] {
  font-family: Poppins, sans-serif;
  border: none;
  padding: 15px;
  width: 68%;
  font-size: 14px;
  margin-right: 5px;
  -webkit-border-radius: 0px;
  -moz-border-radius: 0px;
  border-radius: 5px;
  color: #343434;
  background-color: #fff;
  box-sizing: border-box;
}

#inscripcion {
  font-size: 16px;
  font: Poppins, sans-serif;
  font-weight: 600;
  margin: 0 0 20px;
  color: #000000;
  text-align: center;
}

#formulario-newsletter {
  text-align: center;
}

<div class=“newsletter-wrapper” style="position: sticky; background-color:#c2cdc8; padding:45px 30px 60px 30px; width: 100%; display: flex; flex-direction: column; align-items: center;">
  <div id="inscripcion" style="z-index: 9999">¿Quieres recibir todos mis posts? ⦙ <br> Do you want to receive my posts?</div>
  <div id="formulario-newsletter">
<?php echo do_shortcode('[newsletter_form type="minimal"]'); ?> 
  </div>
</div>