1) On the call screen, check that the call audio is set to the earbuds (Bluetooth icon).

2) If Call Mute has been assigned to a gesture, an accidental tap may have muted the mic – tap the same gesture again to unmute.

3) For WhatsApp, Teams, Zoom etc., allow microphone permission for that app and select Master Buds Open as the microphone in its settings.

4) Make sure hair, a cap or a scarf is not covering the earbuds.

5) Test with a normal phone call to check if the issue is app specific.