Grove - 125KHz RFID Reader - no reading

Hi, I have bought the Grove - 125KHz RFID Reader and I need to use it with Arduino UNO.

I just receive “RFID Test…” message in my monitor serie of Arduino UNO (also with TEST and DEBUG on), the tag that I am using is the typical EM4100 125khz RFID Key (RFID Tag). I am sure that reader is working because when I approach the tag key the green led lights, so, is detecting the RFID Tag but it doesn´t read it.

Is there anything I can do?
Do this RFID reader works only with cards?
Thank in advance

As far as I know, these readers can detect 125KHz cards and keyrings both. Make sure that you are following the code and setup described in the wiki page:

If your reader does not work after all efforts, you can consider using MFRC522 instead.