Hi Clayton, I had the same problem with my 600. I found that after taking it apart and studying it there was supposed to be a plastic point that pierces the cart entry, and it had broken when I had removed the old cart. Only a possibility. Worth a try.
It can happen particularly if you ran the ink dry or left the printer without a cartridge in place.
When you have tried and checked everything else, then put the new cartridge/s in and then switch off.
Do something else until tomorrow, and then you may find that it works normally or an automatic single head clean will be suffient.
I think what happens is that a tiny bubbble develops in the ink channel and overnight the ink filters through to the printhead displacing the air sand allowing the piezo effect to work on incompressible ink