If only one earbud is playing, the two earbuds may have lost sync with each other. Here's how to fix it:
Place both earbuds back in the charging case for about 10 seconds, then remove them together. They should re-sync automatically.
Check both are charged. Make sure both earbuds show a charging light when in the case. One may simply be low on battery.
Clean the charging contacts. If one earbud isn't charging, gently wipe its metal contacts and the matching contacts in the case with a dry cloth.
Re-pair from scratch. "Forget" the CLIP 04 connection in your Bluetooth settings, reset the earbuds, then pair again with both earbuds out of the case.
Remember: Adorn supports mono mode, so it's normal to hear sound from just one earbud if you've only taken one out. To use both, make sure both are removed from the case and connected.
If one earbud still doesn't work after these steps, reach out to support@vionb.com — your earbuds are covered by a 1-year warranty.