You may receive the following message when installing your cartridge. Just click the "OK" button on the first screen. This is just a message that HP has made to try and make you buy only brand new cartridges. This first screen will only appear when you first install the cartridge. The cartridge will still print fine.
Your ink level indicator may show that the cartridge is empty, but it is not. You will know when you run out of ink when the cartridge no longer prints ink on the paper.