Having the same issue - RCA tech support has told me that the Micro USB on the RCT6303W87DK (10", 32G, w/ detatchable keyboard, Walmart) can only be used for charging. I have been debugging the port at a low level and it is not registering properly. Not accepting an address from the host.
I even made a USB A to USB A cable hoping that the full USB port on the device was just a built in OTG adaptor, and that I could debug through that. No luck. Not even any low level communications, so it is not just a OTG style hookup behind the scenes.
I want to be able to use ADB for development, and to root the device.
Since it 'sort' of works (low level) it makes me think that they have disabled the normal functionality of the MicroUSB on purpose, or during manufacture there was a design flaw that is causing communications on the port to fail. Kind of handy if you want to prevent being able to root the device, but again, I am amazed at why they even care? I am just going to take this back to Walmart - if I was able to root it, I would be keeping it and they would have a sale. That MicroUSB port is broken
In fact I already took one back because I figured the port was just broken on the first unit I had. Net result, there will now be 2 units that will not be for resale, and lost sales. Boggles my mind. This is a pretty awesome nice tablet otherwise. Idiots..