This must be one of the most unhelpful messages I have ever seen. What printer documentation? In a split second, how did it suddenly become the wrong printhead? I have yet to find a particularly helpful response in the HP documentation when a standard error message has come up on the little screen (though this is my third HP) and I can not imagine a prospect of getting another HP product.
Didn't cure it for me, but thankyou++ Jay for pointing me to the HP document. The printer is (was) 9 years old and I suppose that it must have been the printhead that had completely failed and replacing it was not an optionl as far as I was concerned. The document was very helpful and well laid out. It is still the case that HP could make it easier (in their manuals)(mine was a paper one - it was that old!) to find the support / explanatory guides.