Today, 03:19
Perhaps try flying with Developer Mode 'Off" as a starting point.
Then in MS Scenario Set up, open up the Weather/Time Icon & in the drop down weather option, select something 'Cloudy' & see if that actually generates clouds when you have the flight set up.
Unusual to be devoid of clouds.
The fact the Active Sky is not showing up suggests there could be something within MSFS where weather is written, or however they do it, that is not triggering.
Do you install the MSFS optional updates? eg, recent South Germany update or World Updates? If you are way behind with those then there might be something in them. ]Long shot]
Can you recall the last time you had clouds & if anything changed between then & what you have now,