I have the exact same issue, since the Windows update 1903 my 6 LL120 fans stopped working (only one lights up). I have two RGB hubs connected to a Commander Pro.
My troubleshooting attempt before reading this thread was to swap the fans in order to identify if any of them was damaged, but all 6 of them light up if they're either in the first or second location, and I tried different RGB hubs too so it's either the Commander Pro (I don't have another one and I won't buy another one) or a software issue.
Pictures: https://imgur.com/a/YEtie9S