Yamaha TW-E7B Noise-Canceling True Wireless In-Ear Headphones (White) - Manual (Page 37)

Power will not turn on
(
There may not be enough battery power left.
Charge this product.
(
“Charging the earbuds” (p.10)
(
The battery power of the charging case may have been depleted while charging the earbuds.
Charge the charging case.
(
“Charging the charging case” (p.12)
(
“Turning on the power” (p.14)
(
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 > Power will not turn on