how do you know if a unit is firmware upgraded or not? by S/N?
Being in US, sending it back to upgrade in China is real expensive.
Just try to enable “Charge and Play” mode. If the firmware on your CMA18P is upgraded one, it will work.
HOW TO ENABLE:
To manually enable “Charge and Play” mode when connected to a USB playback device, long press the Function Button for approximately 4 seconds. The Battery Indicator lights will illuminate and flash, indicating the CMA18P is charging, and audio playback will continue uninterrupted.
Once turned on, this “Charge and Play” mode will remain active until the USB cable is disconnected. In other words, every time you switch USB playback devices, the CMA18P will default back into “Play Only” mode.