printer has ink but is printing blank pages

[mariquin]

I have an HP OfficeJet 3830. My ink cartridges have ink in them (more than half full) and my printer is printing blank pages. I have never had this problem before. I've also not used the printer in months so I thought the ink cartridges might be clogged from googling ink cartridge issues. I used a damp warm paper towel to clean my cartridges and still it isn't working. I have no blinking lights from my printer telling me that there is a print issue or that there is something wrong with the ink, it just simply looks like it is printing the page and as soon as it's done the page is blank. Also, when I go to do a test print, from the settings menu "print demo page" this actually works and prints ink on the paper--that is the only time ink goes on the paper.  Does someone have any other suggestions?

[Valsimot]

Dried ink, replace ink cartridges.