Hello,
Your cart button is there, it's just not visible due to some CSS rules in your "custom.css" file :
.page-item.active .page-link,
.slider-item .sppb-btn-success, .sp-simpleportfolio .sp-simpleportfolio-item .sp-simpleportfolio-info:hover,
.sp-simpleportfolio .sp-simpleportfolio-item .sp-simpleportfolio-overlay-wrapper .sp-simpleportfolio-overlay,
#sp-top-bar, .btn-primary, .btn-primary:hover, .about .sppb-row > div:nth-child(2n), .btn, .title,
a.hikabtn.hikacart, .slider-btn a, .sp-megamenu-parent > li.active:before, .sp-megamenu-parent > li:hover:before, .sp-megamenu-parent > li.active:after,
.sp-megamenu-parent > li:hover:after {
background-color: var(--background-color) !important;
}
Your buttons are now white, with white text.
You need to move your mouse over the button to be able to "see" it.
Regards,