@silvestrejose I think I found the issue you're having, if its the same as mine. My code was all correct, my layers were constructed, everything was fine. I went and built a barebones Leaflet map and added layer control with no issue, so I couldn't figure it out. Eventually I cleared all my code and started fresh and when inspecting I noticed my control div greyed out, sure enough it had a display: none; rule in Windy's CSS which isn't documented anywhere. I didn't even think about this and feel kind of silly for it.
#windy #map_container .leaflet-control-container {
display: none;
}
So you'll just have to override this rule and all will be well in the world. :)