Can't get it to work after refilling. Did this on my previous dell printer a lot and it worked fine. So, is it true that dell has engineered the printer to prevent people from refilling cartridges?

Wm. the scot is going to tell me to buy new dell cartridges but these are expensive and don't last very long.

So, why did the 920 cartridges work when refilled, but the 924 doesn't?