Cannot use Backer Code on PC Steam version

[shellshock]

~2 years ago I played a bit of Shenmue 3 on EGS and entered the backer code that I got in the settings menu to unlock some stuff, among them a black jacket that says Yokosuka on the back. A few months ago I got a Steam copy through Humble Choice and now wanted to play it. However, when I try to redeem the backer code all I get is an error message telling me that "The Steam CD key has not been entered". What am I supposed to do at this point? It worked just fine 2 years ago (see screenshot).

Edit: Apparently you need to redeem a DLC code for each platform which is why I am getting that error. Thread can be closed.

 

[Miraglyth]

For the benefit of anyone searching this topic in the future:

That I could work out, the backer code is just a way to prompt the game to check the user's registered DLC on the ecosystem of the version of the game. So the Steam version checks the Steam library.

Backers were also sent Steam keys for all the DLC rewards their backer tier qualified for so long as they used the updated survey to opt in to requesting a Steam key in addition to the EGS default. If so, check your Fangamer backer page and you should have usable Steam keys that you can register to your Steam account, after which entering the backer code should work.