Yamaha TW-E7B Noise-Canceling True Wireless In-Ear Headphones (White) - Manual (Page 39)

The product does not operate or play back
(
The earbuds are still charging.
You cannot use this product while they are charging. Use the earbuds after charging is finished.
(
There is not enough battery power.
Charge the earbuds.
(
“Charging the earbuds” (p.10)
(
“Charging the charging case” (p.12)
(
The product is temporarily not functioning in a stable way.
After putting the earbuds back into the charging case, wait for at least 10 seconds and then take them
out again.
If this does not solve the problem, initialize (factory reset) the earbuds.
(
“Initializing (performing a factory reset)” (p.45)
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Troubleshooting > The product does not operate or play back