I'm having the same problem on Xbox One. I own Ruhr-Sieg Nord and Long Island Rail Road from TSW 2020, but I only see them for full price in the store (both in-game and in the Microsoft Store). It's as if the store doesn't recognize our licenses. Microsoft store often updates at 7 PM CEST (55 or so minutes from now) so I would definitely wait for that time to see if the DLCs appear to be installed within the "Manage Game & Add-Ons" menu. They should automatically be there, ready to be installed under TSW 2.