I don’t know if this still applies but there was an issue early-on where if you entered the flight with Live Weather turned on it would many times not function. What we discovered was that we had to set the weather to Clear before entering/starting the flight. Once in the aircraft, we would open up the Weather settings from the toolbar and change to real time and real weather. A few seconds after that the appropriate weather would appear.
It could be that the issue was resolved in later updates, but I still use this technique and the results have been decent.