Voice messages won't play through headphones (messenger)

I have the following problem: since yesterday in facebook messenger whenever someone sends me a voice message, I plug my headphones in and play it, but for some reason the sound comes from the speaker. Before it used to play through the headphones without problems. I noticed that when I press the volume keys, it says the sound is identified as "sounds during conversation", which wasn't the case before. Before it came as "medias". This makes me believe the phone thinks I somehow told it to go through the loudspeaker as in normal phone conversations. I'm using a Samsung Galaxy J5 by the way. Thanks in advance!