My printer gives me a message... error 78/77

From that I will take a guess that you have just bought a new cartridge but NOT an epson one.

If this is the case take it back to the shop and get another or a refund (I would take the refund and go elsewhere and never buy that brand again)

If however it is a proper epson original cartridge then take it back as they to can on rare occasions be faulty.

What you are seeing is due to the ink level chip on the back of the cartridge being at fault or dud.