Welcome to the forums, mldisibio
Just to be clear, the "external SD Card" is the one you insert at the bottom of the Reader side on the Pocket eDGe (or top of the Reader side on the enTourage eDGe).
Given that the file explorer isn't showing anything, it could be that the internal memory card or chip has become disconnected, or has failed, although noone in these forums has reported that in the past.
Your best bet is to contact Tech Support via www.entourageedge.com/support
. Their business hours are Monday to Friday, so you may not receive a response until Monday.