Flip open the top of the ink cartridge holder of both the black and
color and look at the underside of the lids. There is a black spring
loaded plastic part that push the cartridge against the contacts.
There is a little part at the front that is easily broken. Compare
with the one on the color one to see if that's the case. If it is you
can put a small piece of plactic (in my case the clip on a Sharpie
marker) or fold a very small piece of paper and put on top of the ink
cartridge against the small plastic at the front of the cartridge so
that when you close the lid to the holder it will force the cartidge
tightly against the contacts.