The red light in the headphone jack means that the MacBook Pro thinks that an optical audio cable is plugged into the port. Try unplugging and replugging a headphone plug into the port several times. There is a tiny sensor inside the port that determines whether the port operates in optical or analog mode. Plugging something analog in is supposed to trigger the sensor and restore the analog signal.
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The red light in the headphone jack means that the MacBook Pro thinks that an optical audio cable is plugged into the port. Try unplugging and replugging a headphone plug into the port several times. There is a tiny sensor inside the port that determines whether the port operates in optical or analog mode. Plugging something analog in should trigger the sensor and restore the analog signal.
The red light in the headphone jack means that the MacBook Pro thinks that an optical audio cable is plugged into the port. Try unplugging and replugging a headphone plug into the port several times. There is a tiny sensor inside the port that determines whether the port operates in optical or analog mode. Plugging something analog in is supposed to trigger the sensor and restore the analog signal.