I can't hear the recording or the MP3

i just downloaded Audacity and I just cant hear the recordings I have or the MP3 i want to use. Is it any setting I have to modifiy?? i can listen everything If I play it in other apps, but not in audacity

Check your [u]Playback Device[/u], especially if you have a USB mic or a USB turntable plugged-in. Sometimes Windows will set the “new” device as the default even when it can’t play sounds.