For secondary accounts I manage for my very casual playing family, I used the free-quests-code (thank you SSG!).
So only Sharns, Ravenloft and the Menace of the Underdark quests were missing to be up-to-date. Though Sharns & Ravenloft series are purchasable, the Menace of the Underdark quests simply do not show up in the store, and the 'buy now' option ingame leads to an empty page.

Is there any fix or workaround for this? Thanks!