Mine did the same thing. Pulled it apart, the microphone cable had broken from moving the boom up and down several times a day over a couple of years. Resoldered that and they were good to go

Also, you can call Jabra and they can help you through other basic troubleshooting. Not sure what their warranty replacement period is, but I had a pair with a similar issue at less than a year of ownership and had them replaced.

Same issue here, boom cable broke internally due to up and down movement to mute. Lasted 2 years.