Our recommendation for SONNET and SONNET 2 users: When you slide the battery cover over the battery pack frame, make sure to close it without leaving any space at the top. The blinking LED indicator lights on top of the microphone cover turn on slightly before the battery cover is fully in place, so remember to still slide it all the way up. This ensures your audio processor will work properly, protects it from moisture, and gives you the best hearing experience. | MED-EL