How do i get sound files in messages on Facebook to play?

my friend just got a new smartphone and on Facebook messaging instead of typing he sends recordings of his voice but every time i click play nothing happens...no sound, nothing. I'm listening with headphones, volume on computers all the way up, everything is as it should i can listen to vidéos and stuff just fine, can anyone tell me how to get the sound to play? he says they play fine on his phone.