Wishlist Button error

Hi there

I think that the problem could be related to your theme’s customizations
Anyway, you can easly sort it out by adding the following CSS rules at the end of Additional CSS section of theme customizer (WP Dashboard -> Appearance -> Customize)

a.add_to_wishlist.single_add_to_wishlist {
    font-size: 0;
}
a.add_to_wishlist.single_add_to_wishlist:hover i {
    background-color: var(--primary_color);
    color: #fff;

}
body a.add_to_wishlist.single_add_to_wishlist i{
    font-size: 14px;
    display: inline-block!important;
    font-size: 11px;
    width: 36px;
    height: 36px;
    background-color: #FAFAFA;
    line-height: 36px;
    text-align: center;
    border-radius: 100%;
    display: inline-block;
    color: #888888;
    margin-right: 10px;
    -webkit-transition: all 0.2s ease;
    -o-transition: all 0.2s ease;
    transition: all 0.2s ease;
}

a.add_to_wishlist.single_add_to_wishlist:after{
    content: 'Aggiungi alla lista dei desideri';
    font-size: 14px;
    text-transform: uppercase;
    vertical-align: initial;
    color: var(--text_color);
}

Here the final result that I got on your site