I am still having this issue. This problem still exist.
Still having this problem in fs24.
Given: Free flight session is started with non-live weather.
When: Live weather is enabled through the weather menu
Then: Live weather is auto. disabled after about two min.
If the weather menu is open, the live weather toggle is enabled, but live weather is not on. You have to turn it off and back on again for it to apply.
This is a huge pain because on long flights, you can’t exit the flight to fix it, and the change in weather affects flight planning and performance.