Help my Kidigi dock not recognized galaxy S3 as a dock

[chris mart]

I have purchased kidigi Dual Desk Dock Charge Cradle on ebay. It's working (I can charge my phone), but my SGS3 not recognized it as a dock. Instead of that, it shows as a charger. If I plug it into the wall socket, it shows AC adapter if I connected it to PC it recognized as a portable media player. I have the latest CM10.1 ROM.

I'm new to dock.This is my very first one. Is it a ROM issue or a dock issue?

Thanks!