Audio DJ/Media Buttons on HEL80

I've seen the thread telling me how to use the Audio DJ buttons. That is fine, assuming they work in the first place . Mine used to work, and now they don't - nothing happens when I press any of the buttons.

I don't know what drives these buttons - I certainly didn't disable them intentionally. In reality, I don't see much use for them, since they simply duplicate functions available via mouse clicks, but I suppose some may find it easier to use the buttons. In any event, I want them to work because they should, and because I MAY choose to use them occasionally.

My machine is a "Clasus Dynamic", which is the Portuguese version of and essentially identical to the HEL80. Today may be the first time I tried to use the Audio DJ since my laptop came back from repair, at which time they upgraded my BIOS (without telling me), replaced my noisy optical drive with a much quieter one, and virtually eliminated the keyboard flex*. I don't know if the buttons already stopped working when I got the laptop back, or if it happened at some other time, which I suppose could have been before the repair or after.

How does one make the buttons work again? Does their functionality depend on some other component?

Any suggestions would be appreciated.

* the redundant details of the repair are provided so that people bothered by similar problems are aware that they can be fixed. The one nuisance that was NOT totally eliminated is the squeaking heard when the right wrist is placed on the front edge of the machine.