If you need your woocommerce cart functions to work while inside an iframe, you have to add this code in your theme's functions file (or plugin's function file):
function iframe_cookies_samesite_filter_wc_session($enabled, $name, $value, $expire, $secure)
{
if ( ! headers_sent() ) {
setcookie($name, $value, [
'secure' => true,
'httponly' => apply_filters( 'woocommerce_cookie_httponly', $httponly, $name, $value, $expire, $secure ),