Why doesn't my Beats Studio 3 want to charge?

Why doesn't my Beats Studio 3 want to charge?
I have had these headphones for over a year, going on two I believe and up until a few months ago they were working fine. But then, after two weeks without using them, they stopped wanting to charge. Now there is no indicator light, no power, nothing. Is this the battery, the charging port, or something else?

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