My AirPort Express cannot be found: "An Errot Occured. Please Try Again."

My AirPort Express (bought in 2011) cannot be found. It worked perfectly for two years until a couple of days ago that it suddenly stopped working. Here're the conditions:

1) All I am seeing now is that the orange light is bliking continuously;

2) I tried to find it using AirPort Utility and everytime I got the message "An Errot Occured. Please Try Again";

3) I tried to both hard and soft reser it. But every time, it returned to the stage in which the orange light is blinking continuously again;

And, bizarrely,

4) I took it to the Apple Store -- and it worked just fine there!!!!

My ethernet is fine (I am using it right now by plugging it directly into my computer). I am connecting using PPoE. Until 2 days ago I was able to plug the ethernet cable it into my AirPort Express, and was able to use both the Airport Express and the wi-fi just fine. No problem at all. Now, something must have hapened, I could no longer use my Airport Express.

Does anyone have any clue what might have happened? Or what can I do to bring it back to life?

Thank you so much.