We've got a couple of HP 110-417cb desktops -- low budget PCs with Intel J2900 CPU, 4GB RAM, 1TB hard drive. Both machines have been in service since mid-June, apparently functioning well, connecting by wireless to network via Nighthawk router. This morning, one of the machines suddenly simply doesn't see the network (the other one continues to work OK). I've gone thru the network setup wizard and it informs me that the Ethernet cable is not connected(!). How do I get the PC to again see the network?