I have added a sollution to V_VAR problem in both my rain and power pulse meter (check these threads). As said above, Homeassistant will not give an answer to these requests if there are no value in the mysensors json file. Either add this in the hardware code or as I did, request a couple of times to make sure you get the value if there is one. Count these requests and set a upper limit, like five or ten reuqest. Once your each this limit, send the value 0 to HA and this will be updated in the json file and start from there.