Epson Printer refuses to print in Black although Black Ink is full?

Model: Epson WF-3640

My Epson printer doesn't seem to want to print with black ink. Pages with only black text come out completely blank, without any trace of ink. According to the display though, my black ink level is almost full. I am low on magenta & yellow, and it keeps telling me to replace cyan, but I would assume that even if those colors were low the black ink should still work, right?

I tried using the automatic printer head cleaning function, but that didn't change anything. Pages of black text still print completely blank. Ironically, there's still a faint hint of color when I try printing color pages (even though all my color levels are low).

Has anyone else had this problem? Any insight would be greatly appreciated.