JBL Vibe Flex 2

As with all in-ear headphones, our range of True Wireless Stereo headphones can be susceptible to a build up of dust and earwax. This can cause low volume on one or both earbuds, or balance issues (e.g. right earbud is louder than the left earbud). To reduce the likelihood of these issues occurring, it is a good idea to periodically clean your earbuds. Clean the earbuds by removing dust and wax after each use, using a pointed toothpick to remove larger amounts and a small amount of rubbing alcohol applied to a cotton swab for final degreasing. Remember to clean the charging points on the headphones and inside the charging case.

If you are experiencing volume or balance issues, always check for wax and dirt in and around the earbud and driver and complete cleaning of the earbuds as described above. If the issue persists, there may be earwax/dirt stuck in the small holes in the grille in front of the driver, preventing sound output. To resolve the issue try dipping the affected earbud tip into a solution of lukewarm tap water and a small amount of dish soap (washing up liquid). The earbud tip should only be put into the liquid up to a maximum depth of 1-2 mm only (see images below). Immersing the earbuds in water or putting the earbuds in water at a larger depth than this could void your warranty. Keep the earbud tip in the water for about 2-3 minutes, then wipe/clean the grille with a small brush (such as a toothbrush). This should remove the wax and resolve the volume/balance issues.

 

Yes, the headphones have Multipoint Connection, which allows you to switch seamlessly between the connected devices. 

Double-tap the button on the right earbud, then on the third tap - press and hold the button for more than 5 seconds (until the unit shuts off). 
This restores the earbuds to the factory defaults.
TWS must be connected to perform the reset, so neither of the earbuds should be off or in the charging case.
It also may be necessary to remove or forget the earbuds from the list of paired Bluetooth devices in order to pair again.

Make sure both headphones are fully charged to ensure that the issue is not due to one of the earbuds lacking power.

Check that the contact points on the headphones and the charging case are clear of dirt, so the issue is not due to the product not being able to charge.

The LED on the headphones will show a blue light when correctly inserted in the charging case.

Try to reset the headphones if the product is fully charged but are still only working in Mono mode.

A reset guide for the headphones can be found here: Reset guide