It use to be that Epson printers, the print head was part of the printer, with HP they were part of the cartridge. So if Epson was not used regularly, you ran the risk of trashing the printer, with HP you just changed the cartridge. My latest HP I think has heads in printer so its no better than Epson, however another HP that I have has separate heads that are consumable - recommend changing after 3 cartridges.
With my Epson, I temporarily fixed it by applying white spirit with brush to bottom of print head. After a while, it was clean and printed perfectly.
However, next time printer was used, again after period of inactivity, I had same problem and could not clear the problem. I dumped the printer. I don't know if I damaged it by putting white spirit on head or whether it was again lack of use, but to this day I vowed never to buy an Epson printer ever again.
Morel of story is to regularly use printer or at least run it through cleaning program.
My latest HP has probably taken its auto clean a bit far now as it cleans itself pretty much every time that I use it, although that's probably every few weeks. Self clean seems to drink ink - cue conspiracy theories.