At first, I did not remove the vent plug because it looked like it had a
hole in it, and the printer graphic showed all red x's in each cart.
Then I pulled a plug and noticed the little hole did not go all the way
through, so I removed all the plugs. Still no luck.
I also
wondered about the seal on the outlet at the bottom... it was a small
square transparent material but I left it on, figuring this was how the
nipple would puncture the plastic and make a tight fit.
Other
Epson printers give the warning message about using a non-Epson cart,
but they would still let me ignore the message and use the cartridge.