Same problem here for the second time. I've recieved a replacement watch. It worked fine till now. No connection on the wire. Only wifi and bluetooth works and loading the battery. I start to lose some faith in de fenix 5x
This is the procedure provided by Garmin official support and it does work: WITH THE DEVICE TURNED OFF AND DISCONNECTED FROM THE PC/MAC, HOLD THE UP-ARROW (CENTRAL BUTTON ON THE LEFT) AND CONNECT THE DEVICE TO THE PC/MAC HOLDING IT PRESSED FOR ABOUT 30 SEC. THEN IT CONNECTS WITH THE PC/MAC AND WILL BE CORRECTLY RECOGNIZED BY GARMIN EXPRESS.
Hope this solution will help you
P.