airport express airplay won't work.

I tried to use the airport express as an airplay connector with normal speaker.

but It didn't work. green light, speaker image and white background check mark on it. but couldn't hear any sound from it.

and when I touch airplay sign, right underneath the airport express check box(right top of the images), automatically turn back to iphone speaker, and it sounds, I don't know why is it like that and, I couldn't find any information about that, finally I got fed up. please give me any clue.

oh, I used earpods by the way, if I use a speaker, will it be different result?