I didn't see a post about missing game info. I don't think this is the only one.

Icewind Dale 2 Complete is missing genre, style, developer and possible critic score.

Do you own it on GOG or a different store? GOG have it on their own store, so I'm surprised it's missing data for that game. But in general I think GOG gets game info from IGDB, so you can try editing the entry for Icewind Dale 2 Complete (https://www.igdb.com/games/icewind-dale-2-complete) and see if it shows up in GOG Galaxy. There's also Icewind Dale II (https://www.igdb.com/games/icewind-dale-ii).