Why does my kyocera 2026 display an error and says add toner even if I have already added toner?

Because your dv unit is not agitating your toner these machines are notorious for this you can take out suspect color dv unit cover the toner hole shake the hell out of the unit smack the bottom a few times put it back in and if that works it will say adding toner it may overtone that color but running multiple copies will eventually clear the excess its best if you wrap the unit in a rag as well as cover the toner hole because toner will leak out when you shake it or replace that color dv unit but they are expensive if you don't know how to remove the dv unit try google or youtube try not to let anything come out when you shake it because there is developer as well as toner in there if you lose too much of that your unit will be worthless it wont ever be able to add enough toner to get add toner message to stop