I tested 68 locations (I took every 100th one from the list of ICAO codes). They're all showing icons except:
DAFH - Tilrempt/Hassi R'mel - Few clouds KEFD - Houston / Ellington - Few clouds KOVS - BOSCOBEL AIRPORT - Few clouds
So it looks like "Few clouds" is the problem.
I tested 68 locations (I took every 100th one from the list of ICAO codes). They're all showing icons except:
DAFH - Tilrempt/Hassi R'mel - Few clouds
KEFD - Houston / Ellington - Few clouds
KOVS - BOSCOBEL AIRPORT - Few clouds
So it looks like "Few clouds" is the problem.