Why has the left side of my beats x stopped working?

Why has the left side of my beats x stopped working?

i just got these for christmas, so three days ago and they have been working perfectly fine. i was wearing them and i decided to lay down while talking to my friend and the left side of them just stopped working. is there anything i can do to fix this problem? i have looked online and the only problems i see people have are with the right side.

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