==== Update 17:43 CEST ====
The issue is now resolved, our apologies for the trouble caused to those impacted by it.
=========================
We are currently experiencing some issues with Steam. The issue is that people can't buy Vermintide 2 without owning Vermintide 1.
The problem has been identified and we are working with Steam to get it resolved as soon as possible.
We thank you for your patience.