I you thump, shake, and sometimes resort to squeezing the converter or cartridge, then here is a tip for you.

One reason fountain pens clog is there must be an equal exchange of air for the ink that flows out - if air is blocked from coming in, ink won't flow out. Take it all apart and soak the nib part(s) in Windex overnight, then rinse off with warm running water. This will clean out any bits of dried ink and should help.