On HP printers, they only keep track of the last 2 cartridges installed - so you can take out the printer backup battery or install the old cartridge again, twice, then the new one again. For the Epsons, you can get a little gizmo on eBay for about 6GBP which will reset the chip in the cartridge so it thinks it's a new one.
Bill
March 2007
try taking the cartridge out and putting it back in. ( using the maintanance software ). This worked for me.
anon
March 2007
it may be that you have a budget cartride that does not include the relevent electronic chip to tell the printer its new and installed - if so try a genuine cartride and see if it makes any difference - particularly if you have updated your printer software recently
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Try fixfault.com to fix printers.