When plugged in - can you get any info in the display by touching the volume control, moving your finger clockwise?
If so, then it may be that you have left it plugged in for an extended periode of time without any use. Somehow the intelligent battery charger may have drained the battery and operation is not possible. A possible remedy is to plug it in, try to operate the volume control and see if you can get any info in the display - if you do, the product will consume enough power for the battery charger to "wake up" - please note that this charge will take hours. It did happen to mine, and it used 12 hours to charge the battery. Once the battery was fully charged the unit worked perfectly.
And, yes, I left it plugged in for a couple of months without any use...
Roger