Make sure the ink cartridge is aligned correctly, I once had this problem because I did not insert the cartridge correctly or didn't remove the protective covers.
Did you recently change ink brands from HP? HP Printers only recognize specific brands. I tried some cheap and off-brank ink and my HP printer would not pick up the ink levels of a cartridge and often said it was empty when it wasn't.
Ths is twice that I change my ink cartridges using the same ones all the time, never the refilled ones.
My HP Photosmart C6380 All-in-one prints fine, and on the Printer's wee viewer window it tells me the following: "one of your cartridge is out of ink, please see your PC to know your ink level"
It used to show on my PC's right bottom corner but it no longer does.