There is no sound from the (L) left unit or the (R) right unit.

Try the following:

• The smartphone and the headset (both the (L) left unit and (R) right unit) are turned on.
  When the battery of the headset is completely discharged, the headset turns off automatically. Place the headset in the charging case and allow it to charge.
• Depending on the smartphone app (which requires HFP (Hands-free Profile)/HSP (Headset Profile)), you may only hear the voice from either the (L) left unit or the (R) right unit.
• When using only the (L) left unit or the (R) right unit with the Google Assistant function enabled, use the unit on which the Google Assistant function is enabled.
• When using only the (L) left unit or (R) right unit with the Amazon Alexa function enabled, use the unit on which the Amazon Alexa function is enabled.
• Turn the headset off, and then on again.
  Put the headset in the charging case and close the cover. Then remove the headset from the charging case and confirm that the indicators (blue) on the (L) left unit and (R) right unit are flashing.
• Reset the headset.If resetting does not work, initialize the headset.For details about resetting and initializing your headset, refer to the Help Guide supplied with the headset.