On my new Logitech keyboard, the number side is not working and the accents for the Spanish words either.
I agree with all the points made by Jim, Hovsep and Alan. First, download a driver, if one exists. Then, check your Regional & Language options to make sure the Spanish layout is installed, finally, check the status of NumLock. If the keys still don't work, there could be a fault with the keyboard - try it on another PC and see if it works, and return for replacement if required.
If you haven't done so, install the driver available from Logitech support for your particular keyboard.
Alan advise is good one, also go to device manager locate the keyboard driver, right click and choose uninstall (do not delete) reboot. This can bring to initial state so you can carry your work to Spanish layout
Check that the NumLock light is on, if not press the NumLock key once and it should light up.
In the Control Panel click on devices and Printers then right click on your keyboard icon and select Language Options. Check that you have the right language install for the keyboard, in your case Spanish.