WH-1000XM3 left ear suddenly not working (noise reduction and audio)

[offtherecord]

From one day to the next, the left ear stopped working. When connecting the headphones through Bluetooth, the left ear doesn't seem to connect. I tried with a cord which brought the audio back (to both ears), but no noise reduction. Have restarted and upgraded. Any other advice? 

[Ragmatras]

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When I checked settings on my MacBook somewhereI found the balance was focused on the left ear, was able to switch it back and it worked again

[HannahEd01]

Hi Ragmatras, thank you for sharing this useful advice.