The shop asks for 1 key and 5 refined metals , but when I proceed this error pops up .
And I'm pretty sure that I have the right items (1 key and 5 refs), as you can see from my own inventory http://steamcommunity.com/id/Miskude/inventory/ .
I don't know what to do.

I have the same problem. :(

I'm also still having this problem.