Beats Solo 2 doesn't turn on when not plugged in

Hi cs_damien,

We appreciate you reaching out to us.

We’d like to gather additional details that may help us be in a better position to assist you.

Have you had the chance to try multiple chargers?

If yes, the next step is to reset your Beats.

1. "Make sure your headphones are not plugged in to your USB charging cable.
2. Press and hold the power button for 10 seconds.
3. Release the power button.
4. All of the Fuel Gauge LEDs blink white, then one LED blinks red. This sequence happens three times. When the lights stop flashing, your headphones are reset."

Also, please check out the steps under the "Other things you can try" section.

You can use the article below as a reference.

Reset your Beats on-ear or over-ear headphones - Apple Support

Take care!