Are you playing in TV mode?
No sound will come out of the Nintendo Switch console speakers when the console is in TV mode. Please check the volume on your TV.
Is the volume low on the console?
Use the volume buttons on the console to turn the volume up or down.
Is your hand or a screen protector covering the speakers on the console?
Are headphones connected to the console's audio jack?
No sound will come out of the console speakers when headphones are connected.