Bizhub c352 not printing black. I change the catridge still not change. please help.

The toner is not install properly. At the front end of the toner cartridge has an opening and a slide cover when you push the cartridge. underneath is the black developer unit which it has same opening and a cover some tines the Spring of those two opening cover might come of or tech intentional removing the spring so the opening stay open. but those two opening cover have to engage to open each other to open permitting the toner to drop to the developer unit. examine the the front end of the developer unit and toner cartridge slide covers.