No sound at all

hold down the option key on your keyboard and then press the volume up or down button on your keyboard. This brings up the sound preferences pane. Click on the Output tab then make sure your headset is selected as the output.

I’m happy to help further over the phone at https://www.6ya.com/expert/matt_7e951e081251ffbc

Open System Preferences, and click on the Sound icon. Under the Output tab, make sure "Internal Speakers" is highlighted, and the "Output volume" slider is not all the way to the left.
If that is the case, take it to the Apple Store and have a technician look at it. Since you only got it a few hours ago, they'll fix any issues free of charge. (It's under warranty for a year)

Option Click on the Speaker Icon on the menu bar to Check you Sound Output options.

Current models of MacBook have dual-phase audio out jacks that work both with electrical and optical equipment. If a headphone plug or other foreign object is inserted into the jack too firmly, or is slightly oversized, it can permanently bend the components that detect which kind of plug is inserted, or if there is no plug inserted.
There are four steps the owner can take before taking the machine in for service:
Make sure all software updates have been applied.
Check in System Preferences: Sound: Output that sound output is set to "Internal Speakers".
Use the F12 volume key to set the sound to maximum.
Reset PRAM by shutting down the MacBook, then pushing the power button to boot it and immediately holding down the four-key combination command-option-P-R until the boot chime is heard three times.
If this does not correct your problem, your logic board may need repositioning or replacement.

Try the following:

1. Select System Preferences from the Apple Menu.
2. Select the Sound icon.
3. Click the Output tab at the top of the window
4. Highlight the option that is not the Internal Speakers.
5. Make sure the Output Volume is not set low and that the Mute checkbox is unchecked.
6. Close the Sound window. (via Red Radio Button, Top/Left of window).

Try it again and see if you get sound this time.

I hope this helps. Regards,

it can be the cooling system, but you will have to show your machne to a reparator.

Have a look down the jack socket where you would plug in speakers or headphones - is there a bright red light?
If there is it means that audio is being routed through the digital output not the analogue (which includes the internal speakers)
Go to system prefs and check on Sound - last icon in the second row.
There should be at least three output options listed, digital, line out and internal speakers. check Internal speakers and that should be it.
However. Just lately I have seen 2 white macbooks that have only DIgital listed and have been unable to fix it.

try blowing hard into the output socket, then plugging and unplugging your headphones.

Sounds like the cutout switch in the output jack is stuck open, it is a techy fix sorry (at least it is not a board failure)

Omigod, that worked!!!!