Printer colour cartridge not recognized

[sizk]

Hi,
after my parents changed their printer (HP Photosmart 7760) cartridges they could print a few pages normally but suddenly it began printing using only the black cartridge. The colour one doesn't even show up on the panel indicating the state of both cartridge.
How can they fix that?

Thx for your help

 

[patrickv]

some suppliers sell fake cartridges, and it worns out in less than a month.
i had this issue with a hp laserjet 1020, they sold us a fake toner, it started printing and after 2 weeks, paper would go in and come out empty, and it toner itself still was in good condition.
in my opinion tell your parents to bring back the catridges (if still on warranty) and test it at the store

 

[sizk]

I'll tell them to try that but doesn't the fact that the cartridge doesn't appear on the 'ink levels panel' (sorry for the inaccuracy of the vocabulary, do you see what I'm talking about?) suggest a failure of the printer itself?

Thanks for the 1st hint anyway.