I don’t own these so can’t advise authoritatively.
Short version - TWS buds is a wrought with risks and easily breaks.
Long version - This kind of problem can arise if the buds got out of sync with each other and/or the data connection (which is other than headset and headphone) failed and/or something else nearby paired with one of the buds.
So what you have to attempt to do is get the buds to sync to each other and/or delete all historical records of pairings and/or remove the other rogue connection. Can’t tell on an individual case which so these is the fault so an overkill try-everything approach.
- (ensuring the reset signal gets to both buds) Clean the case inside buds connection and the buds. Use isopropyl alcohol. This step removes the possibility the case is not sending the reset signal to both buds. Let the case and the buds dry.
- (checking the case is sending reset signal) Plug the case into power, ideally for hours if you have patience.
- go to somewhere away, somewhere else, in case something rogue connected to one of the buds. A park would be a good example to visit.
- Follow the reset instruction.
- Wait. At least a minute. Some have found the reset takes longer and have rushed so not done a reset properly. Hence after reset (to force at least a minute) also do
- delete phone pairing, turn off phone bluetooth
- If on Android, delete the cache. Boot to recover, wipe cache (not data), boot. This will have killed a minute probably.
- Turn on bluetooth. Pair.
- It works now?