Thank you for your reply. Actually it was just a class written in a wrong way. This happens when you have looked at a code so many times that you no longer see the details. 

Hi all,I'm struggling to add an additional product to cart via API, but it's not working. The scenario has been already discussed because it's the classic embroidery that should be added to a main product when a checkbox is checked.I've created the e...

Yes, both of them will make the trick.

In the previous page you find the solution for the desktop.

In header.liquid find this code <div class="site-nav--mobile text-right"> Then below you should find a line starting with <span class="cart-link__bubble  Replace it with <span class="cart-link__bubble{% if cart.item_count > 0 %} cart-link__bubble--vi...

You should replace this, from the previous answer<span class="cart-link__bubble{% if cart.item_count > -1 %} cart-link__bubble--visible{% endif %}">{{ cart.item_count }}</span>to this<span class="cart-link__bubble{% if cart.item_count > 0 %} cart-lin...