Can not recognize Nexus 7 2013 version with USB
I have had this problem on a labtop of my mom's. Maybe there is some security feature on the mainboard, I could not try it on this labtop because it is not mine, but that might be the issue. Look out for secure boot for example. (it would be interesting to know if it is a Dell, if yes this could be an issue referring to the company or kind of bios/uefi) I have tried it on another pc, desktop this time and I did not have any trouble. So if there is no option to fix it in the bios, just use another pc, (preferably a desktop) and flash on this system if you can.