Beats Flex blinks red and then stops showing a light all-together whilst plugged in

Hi katrelln,

Thank you for participating in the Apple Support Communities. We understand you're unable to charge your Beats Flex. We recommend trying a different cable and power source. You may want to try resetting your Beats as well and then try charging again. Here's how if needed: Set up and use your Beats Flex earphones after service.

"Turn on and charge your Beats Flex

The power button is on the right control module. Press and hold the button for 1 second to turn your earphones on or off.

To charge, plug your earphones into a power source using the included USB-C cable. Your earphones provide up to 12 hours of playback from a full charge. 

When your earphones are turned on and set up, the LED indicator light on the power button shows how much listening time is left: 

• White: more than an hour left
• Red: less than an hour left
• Blinking red: needs to charge"

Reset your Beats Flex

1. Press and hold both the power button and the volume down button for 15 seconds.
2. When the LED indicator light flashes, release the buttons. Your earphones are now reset and ready to be set up with your devices again."

If that is not working, you can look into your service options as explained here: Beats Repair & Service - Apple Support.

We hope this helps.

Take care.