At times some ink jet cartridges with the print head attached to the cartridge might not print right away.
This sort of thing mostly affects cartridges such as HP, Lexmark or Dell.
Generally when this happens it is due to the ink not getting down to the print head.
This is because the cartridges might have been kept upside down or flat and the ink settled in the cartridge away from the the printhead on the cartridge.
To get the ink flowing to the print head take the ink cartridge out and stand it upright. Then get a damp paper towel and let the print head sit on it.
This will bring the ink down to the print head. Once you see ink on the paper towel it is ready.