Disclaimer: I am not responsible for any damage or misconfiguration to your PC. Your mileage may vary.
I purchased the Premium Deluxe version of the simulator on Day 0, Hour 0. I got plenty of CTD’s on short finals, setting up flights, etc., but my live weather worked pretty well…for about the first month.
Then my weather started acting funky: I was unable to change planes or even look at the Nav Log without my weather reverting (on spawn-in to the ramp, gate, or even straight to the runway) to the stupid 3kts out of 225. Clear skies, 29.92 and CAVOK.
This was…endlessly frustrating…to me, as “Live Weather,” or at least a near-approximation of it, is of primary importance to my flight simulation experience.
I uninstalled and reinstalled the sim about five times over the space of a few months, but no joy. The “Repair” option did not work for me; neither did “Reset.” I came close to hanging 'em up and rage-quitting MSFS.
I hung tough, though, and gutted it out. I was able to get live weather on my first flights, then had to exit and re-enter the sim for subsequent flights or if I wanted to change aircraft.
I waited until the UK & Ireland World Update 3 dropped and decided to give reinstalling the sim one. More. Try.
And I am very glad I did! I get Live Weather 100% of the time now, and am able to look at the Nav Log, change altitudes, and change aircraft (with a caveat, below) at will. No more 225/03 and clear skies!
Here is what changed: This time around, I completely uninstalled the simulator first. I uninstalled through the Windows Search dialogue, as usual…and then made sure all remnants of the sim were also gone.
What do I mean by this?
MSFS resides, as near as I’m able to tell, in three locations on my PC:
C:\Users<Owner>\AppData\Local\FlightSimulator
and
C:\Users<Owner>\AppData\Local\Microsoft\WindowsApps\Microsoft.FlightSimulator_8wekyb3d8bbwe
and
C:\Users<Owner>\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe
The last two locations are zeroed out when I do an uninstall, but the first is not, from what I have seen. At any rate, ensure that all three locations are no longer there after the uninstall, then reboot.
Something else that I changed was that I reinstalled the sim to root. That is to say, I created a folder called MSFS2020 on my root drive (i.e. C:\MSFS2020) and pointed the installation path to it.
I installed the initial bulk files (~130GB or whatever), then went to Content Manager and installed the additional files (all the updates), then took it all the way down to the runway (the TBM 930 down to wherever), exited the sim, then rebooted.
Voila! I am now able to look at the Nav Log and change alts, and also am able to change planes (and here’s that caveat) in the Hangar (not from the World Map) to my heart’s content. And I get “Live” weather 100% of the time. 
I hope this helps.
-Whiskey