Live weather server is not down, you can check status here: Online Services Monitoring
The point is that there is an issue where the clouds stop to be injected for some users (wind/pressure are injected) and it is inconsistent. For some, disabling the IPv6 fix the issue but not for all. No one knows the root cause, this thread is feedback-logged what means devs are investigating.
You can also check that forum https://forums.flightsimulator.com/c/self-service/weather/328 where many users have been reporting the issue of no Live weather at all and you can find some recommendations to check some setup that in some cases allowed users to get their Live weather and clouds back.