My Brother J6920DW printer has stopped printing using the black cartridge. The magenta, yellow, and cyan cartridges still work properly. The black cartridge is no longer working even though I installed a brand new black cartridge and all indications show 100% for the cartridge. Needless to say not only is black-white printing failing to print anything at all but even color printing shows very light because no printing using the black cartridge is succeeding. Any ideas how I might be able to fix this would be appreciated.