Canon Pixma iP1900 printer not recognising compatible cartridge

[Quinky]

I have a Canon Pixma iP1900 printer (in the UK). When the ink ran out I replaced both cartridges with Tesco compatibles. The C40 (black) works fine but the C41 doesn't print at all, not even a hint of ink appears. I put a tissue to the printhead and all 3 colours flowed forth, so the problem is presumably electronic - the cartridge is not being recognised. How can I overcome this?

Thanks.