lol,sorry about that but it was a straight question so i answered.
you could try cleaning it as steve says it does work in alot of cases.but be careful,dont rub it too hard if its a carbon membrane! you could rub it off! a light clean should be enough.
i found soapy water works a bit better and use a lint free cloth,after let it dry fully.
there are a few different types of a2000 keyboards but some dont have a membrane and use pcbs,if you take it apart and take a picture that may help.
problem is we can only suggest a way forward on this,as we dont actually have in front of us to see the problem close up.
its definitely going to be a contact problem as these are just matrix's to a keyboard encoder.
you can even trace the signal back from the two contacts for that key i.e: trace the two contacts back through the matrix and short the contacts at the key if the multimeter beeps on diode test it could be the plunger you could try cleaning that as well its mostly carbon,but dont be worried if its about say 100-200 ohms that should be normal.
and test if the trace is intact,some have diodes on the keyboard anything to with that key should be tested.
i also suggest a large bowl or box to put all the parts in,theres alot of parts in one of these you dont want to loose any of them...