Computer doesn't recognize unit when connected. I know that it is not the connection on the unit,

Question

I know that it is not the connection on the unit, nor the usb port. USB port works fine, and the connection on the unit also works fine as the charger too. I bought a new data link cable thinking that it was the cable, not the case. Computer doesn't recognize unit anymore when connected. Was doing so for months, then it stopped. Please help!