Zanussi softener not going down

I’ve had my zanussi machine for about 5 years and normally when the softener doesn’t go down like everyone else I give the drawer a thorough clean but this model has a plastic cover over the small holes where the water comes from, you can’t remove the cover so I’m guessing it has got to the point where it is bunged up, this plastic cover seems to be what is stopping me cleaning it but we’ve taken the top off the machine and it covers some electrics in the top of the machine and has lots of screws to hold it down, I just wondered if anyone has any tips as I’ve tried ever way to try and remove the lovely black Cloggy stuff. Thanks