The left earbud of my new headphones wont work

looks like holding for 5 seconds enables manual pairing of each earbud
https://manuals.plus/jbl/vibe-300tws-true-wireless-earbuds-manual#manual_setup

hi there, I had skull candy earbuds in the past. The problem is that the left side has a short in the speaker. It means that you need to get a new pair of earbuds as they are not fixable.

Well, I had the same problem with the right earbud. Luckily I was under warranty with Target, so they told me to contact Bose. I did and they had me send in the headphones (to make sure I waas telling the truth) and about 2 weeks later I got my earbuds back. Their customer service is excellent, so that's what I would reccomend

They should come apart right where the metal meets the plastic, just below the buds themselves - be careful, one set like that I took apart were actually surface-mounted to the housing, there weren't any leads to repair...

Out of the box or before using it, you have to charge the headset for about 4hrs or until no light on the headset (red if it's charging). Then try using it again play around with the volume. If you encounter the same thing then you have to replace it at the store.

I have this problem all the time with my JVC earbuds. This may sound a little gross but it will work. I put the ear phone in my mouth and **** on the end of it pretty hard. What I have found is that sweat or even wax will plug the little hole and prevent the sound from coming out.

It is likely that your right stereo channel has either been severed somehow or there is a severe short in one of the cables. What you can try to do to test this theory is first turn on your music. Then wiggle the cable at the very base of the right earbud. If nothing happens wiggle the cord right where it connects to the stereo jack. If still nothing happens run your fingers along the right earbud audio cable bending and twisting it. If at any point you hear music again then you likely have a short. If it is near the earbud then it is going to be difficult to fix since these earbudfs have a large gauard. If the short is at the stereo jack then the fix is simple. A standard 1/8" stereo jack can be purchased from any electronics or audio store. You can then fairly easily seperate teh old stereo jack and solder this new one in place. Search the internet for tutorials on how to do this if need be. Even if you do not get any kind of sound when wiggling it at the base of the jack this is the most likely culprit since this is where most of the stress on the headphones occur. Be wary though, if you do attempt a stereo jack repair you will void whatever kind of warranty your earbuds may have so check before you try. But, in teh end you may end up saving a 60-100 dollar set of earbuds for 5-8 dollars. Hope this helped.

The headphone jack might need to be replaced check here
http://store.ifixipodsfast.com/index.php