Heat map tooltip issue

When I am adding to the tooltip property .attr(“data-year”, d=>d.year) all my map and data dissapearing. What’s wrong with this please

 var tooltip = d3.tip()
                .attr("id","tooltip")
                .html((d) => d.year+" - "+ (months[d.month-1]) +  "<br>" + d3.format(".2f")(json.baseTemperature + d.variance) + "&#8451;" + 
                     "<br>" + d3.format(".2f")(d.variance) + "&#8451;")
                .offset([5,0])
                .direction("s")
                // .attr("data-year", (d) => d.year);........on this line everything dissapearing

code: https://codepen.io/jvin/pen/yLBxpQP?editors=0010