My printer won't print because there is more than one inktank of the same colour

Whenever I try to print, I get a message that there is more than one ink cartridge of the same colour (black). That's how it's supposed to be and this was not a problem when I used the printer from new in the first 6 months. THe error message says that only one ink cartridge should be used each time suggesting that there is nothing for me to do but merely a warning message that it will only use one of the two black ink cartridges. When I click OK, the message reappears and I am stuck in a loop with the only option being to cancel the print job. I reinstalled the printer twice so far with no effect.

Can anyone help?