A search does not turn up anything concrete for these speakers.  Do you have the actual Dell model number rather than the part number.  This is mostly a users helping users forum, with a Dell moderator.

In general, check all cabling, reseat the connection to the PC (unplug then plug back in).  Plug the speakers into the front headphone jack and see if you get audio.  Finally, may be a PC issue, check the audio playback device, it should be set to "Speakers".  Also, plug a headphone into the rear GREEN speaker jack and see if you have audio, that will determine if its the PC or the Speakers.

CN-0N1818 Zylux Multimedia Computer Speaker System Powered Subwoofer A425

A425 Diagram
A425 ON1818

https://www.amazon.com/Dell-A425-Computer-Speakers/dp/B004572U48

I would try re-seating all plugs.

Yes, PC speaker and Subs sets can malfunction. I've fixed a couple in my days.

However, before I wrote-it-off ... I would test with some other know-good machines or devices.