eStudio 4511 Install new Black toner message

[Guest]

I put a new cartridge, although it still was half full, but nothing...the same message. I vaccum the black toner cartridge receptor and it worked for 50 copies more. Then I changed the black developer unit (not new but working in another machine - same model) and it worked for another 200 copies. Now I have the same error. (there's no code.. just the message: install new black toner cartridge.)
Any help will be appreciated.

[fireater]

have had the toner hopper break the auger you my need to check...
have u checked to see if the bottle turns when the copier asks for toner?
could also be the dev sensor circuit (i see u replace the dev unit...did u balance the dev? )could be bad connection