I also noticed issues when trying to run the Case 5 DLC. I installed the .WAD without issue, and the extra "PWAA Pay & Play (E)" save data entry appeared as expected, however no "Case 5" option appeared in-game on the same screen as "New Game / Continue" (where it should be).
There is always a "Buy Case 5" option on the main menu, so I decided to click it - I got an issue which I was able to reproduce in Dolphin which I
suspect is related to having never generated Wii Shop credentials (since I had never opened the Wii Shop Channel) on my Wii U.
Reproduction of the message:
I then opened the Wii Shop Channel, which didn't do much until I plugged in my Ethernet cable. I did that, and then after a minute or too I was able to browse the Wii Shop.
Now, if I launch the main game, choosing "Buy Episode 5" brings me to a screen which claims two things:
- the cost of episode 5 is 0 points
- the case is "already downloaded"
Regardless of whether I "continue" or "quit" this process, the case is now directly selectable from the "New Game / Continue" screen.
I did a bit more experimentation, by removing the save files (one of which was this "Pay & Play" file), reinstalling the DLC wad, then relaunching the game. Here, Case 5 was again immediately playable from the "New Game / Continue" screen.
I believe that the DLC only works if the Wii / Wii U has an 'activated' Wii Shop Account, with a valid number of Wii Points (even if 0).
I believe that running on a Wii / Wii U (or Dolphin) which has not first "authenticated" itself with the Wii Shop must have some variables or credentials "undefined" which prevents the DLC from being properly detected.
This could be a huge problem once Nintendo take the Wii Shop down next year. All thoughts welcome.