I had the same problem with my B110a. Unable to get the black ink to print.
Tried all the suggested tests but no luck.
As a last resort, I removed the black cartridge. I then got a cottonbud and cleaned the nozzle where the ink pad on the cartridge touches the corresponding hole in the printer.
I replaced the cartridge making sure it clicked into place firm ly.
I then printed off a document and surprise, surprise it worked perfectly. It's worth a try - maybe this is the answer.
Machine now working properly.