internal speakers on my Mac aren't working

If you tried the troubleshooting mentioned in this related article, and you still can't use the internal speakers, you should contact the official Apple Support about that.

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First, disconnect any cables from the USB, Thunderbolt, or 3.5mm audio ports on your Mac.

1. From the Apple menu , choose System Settings (or System Preferences).
2. Click Sound.
3. Click the Output tab, then select the built-in speakers. If you don’t see built-in speakers as an option in the Output window, contact Apple Support.
4. If the Output volume slider is set low, move the slider to the right and test again.
5. If the Mute checkbox is selected, deselect it and test again.
6. If you still don’t hear any sound, contact Apple Support.

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copied from the related article: If the internal speakers on your Mac aren't working - Apple Support