A configuration parameter which sets the error message text
that appears in data-ajax-cart-errors containers
when a Shopify Cart API Ajax request is failed and doesn’t have any error description,
or when the request is not performed at all due to the Internet connection.
By default, the text is “There was an error while updating your cart. Please try again.”.
Use the conf method of the liquidAjaxCart object to set your value:
liquidAjaxCart.conf("requestErrorText", "My request error message");