are you saying the ink lvl indicator is showing no ink, or there is no indicator at all?
If there is an idicator and its empty, but you know there is ink in the cartridge, did you take the cartridge out after you put it in then installed it again, this will lead to a no show on the indicator. Like Mr Howard said, you'll need the HP drivers to show the ink lvl.
HP no longer supports those drivers as XP has them, so....