Keyboard attached with USB not recognized at startup

When I power on my iMac it does not recognize the keyboard plugged in with a cable. It starts looking for a Bluetooth connection and doesn't find on so the system will not allow me to complete login since keyboard not recognized. The keyboard is 5 years old and has worked fine until this week. Settings have not been changed Could the keyboard be broken or need replaced? I was able to connect with the bluetooth keyboard the iMac came with and it woks but I prefer the larger keyboard with the number pad etc.

Thanks