My printer was working fine - it now says 'service required'

Please can you help. I have been using my printer fine. I replaced a cartridge on Friday, it did one print then came up with the printer message 'service required'. It seems I need to reset the counter and for this I need some kind of code. Are you able to help or advise?

many thankts

Re above post - my printer is an Epson Sylus Photo 1400