After a complete manual cleaning of a 9800 (following your instructions) + cleaning with piezoflush cartridge, my nozzle check (with piezoflush )was perfect.
My problem is after, with the piezo ink cartridges. I can’t get a clean nozzle check. Already did some cleaning, check the cartridge again (maybe some air inside, but no), clean again the printer’s capping station etc, no way, impossible to get a clean nozzle check, even after different cleaning cycle (sometimes it’s worst). I get after each cleaning the message “error cleaning”. This is a the second time that I have a perfect nozzle check with only piezoflush and a bad one with the piezo cartridge. Some idea?