We're sorry that you're having a problem with the sound. Depending on the smartphone app or computer application (for which HFP (Hands-free Profile)/HSP (Headset Profile) is required), you may only hear the voice from one headset unit. 1-Charge the earbuds. 2-Reset (restart) the playback device. As the playback device may not work temporarily, switch the device off and on again once. 3-Clear the Bluetooth device information of your playback device. 4-If the earphones are connected to a computer, check the following settings: For Microsoft® Windows® 11 operating system: -Open the Start menu and select Settings. -Select System. -Select Sound. - Scroll down to the "Advanced" menu and select "More sound settings". - On the "Playback" tab, select "Headphones" and click "Set as default device". For Windows® 10: - On the right side of the computer screen, right-click on the speaker icon. -Select "Open sound settings" and then -Select "Sound control panel". -Select the "Playback" tab to display the device list. -Select the headset labelled "Handsfree" and click on "Set as default device". -Select OK to close the settings screen. 5-Initialise the earbuds. If the problem persists, we recommend that you contact us directly. You can find the contact details on our support page.