Unfortunately, due to a major change in the Amazon web API, our Amazon search plugin (which is quite dated, I'm afraid), is no longer functional. On the upside, this is probably a good thing, as I've needed to fix it for some other reasons and was simply stalling that off until I got some free time. Now, I'll have to work over the code.
If anyone has suggestions for features (and I make no promises), please feel free to post them in a topic in the forum and I shall respond as time allows. Even if I just address the current limitation to restore functionality, I may very well implement some enhancements in the future.
Apologies for the inconvenience. I hope to have something functional in the near future.