kick it real hard.
but seriously....
well, you've proven the keyboard works, and at least one functional cable. good start. now we look at the machine you use normally. is there a port you normally plug it into? it is possible that the port could have malfunctioned. have you tried all USB ports? The drivers are installed in the system (we assume at this point, correct?), so we should at least get a prompt to install new hardware. OR is could get recognized and installed automatically. Point is, there should be
something that lets you know you just plugged it in. A noise, a dialog box, something. If not, keep moving.
On the same note, if you get no notification that you just plugged it in, try another usb device in those same ports. USB mice work well. they are automatically installed and work when plugged in without the need to download drivers. A cheap, corded USB mouse is the best test. This will prove that the hardware in the machine works.
check that out and see what happens.