If you're having trouble with the microphone on your Logitech UE Mobile Boombox, try the following:

• Make sure you're trying to stream audio from the correct device (if you've paired multiple devices). See answer 360023249694 for help.
• Disconnect any devices from the 3.5mm auxiliary connection — the microphone won't work with a device connected to this jack.
• Make sure your Bluetooth device is within the range of your mobile speaker.
• Check that you haven't activated mute on your phone.
• Turn off your mobile speaker, restart the Bluetooth connection on your device, and then turn the speaker back on.