Thanks for contacting the community. I'm very sorry to hear that you are experiencing some difficulties with your left earbud of your SoundSport Free Headphones.
I would love to do what I can to assist you with this matter.
Does there appear to be any signs of power within the earbud?
Have you tried connecting your headphones to another Bluetooth device?
Something that I would firstly suggest is that you check for any available firmware updates for your headphones. This can be done via a computer using a USB and visiting our firmware update website btu.bose.com. This will provide you with instruction on performing an update.
Please let us know how you get on. We would love to do what we can to get this resolved for you.