When you are in a call, it is normal that sounds comes only from the right earpiece. The microphone is also located on the right earpiece.
There are several possible reasons. Below are the steps to solve the problem.
When you are in a call, it is normal that sounds comes only from the right earpiece. The microphone is also located on the right earpiece.
Place both earpieces in the charging case and charge them.
Note that the headset is designed for connecting to only one Bluetooth device at a time. When you reconnect the headset to your Bluetooth device, make sure the Bluetooth function of any other previously paired/connected devices are off.
Factory reset the headset.