the module should update every hour automatically, for testing purpose you could try in the config.js
{
module: 'mmm-weatherchart',
position: 'bottom_left', // this can be any of the regions
config: {
country: 'Germany', // as determined above
area: 'North_Rhine-Westphalia', // as determined above
city: 'Duisburg', // as determined above
updateInterval: 15 * 1000,
hideBorder: true, // whether or not a border with city name should be shown
}
}
this should update every 15 seconds then open the dev console (Command+Shift+I) and see in the network tab if the picture is getting reloaded all the time or you having any errors in the console