Clogged P800 - need help

Hello. I have a P800 printer with Piezography inks which has not been used for several years…
I removed the ink cartridges and put in a set of cartridges with the piezoflush cleaning fluid. I did several head cleanings with the printer. But the cleaning liquid does not yet pass through all the circuits. Some look completely clogged, but I don’t know where.
I watched the video about cleaning with piezoflush (Epson small format printer maintenance - YouTube). I followed the instructions but I couldn’t reproduce the step (around 6 minutes in the video) where you force the liquid to go to the printhead by pushing it into the cartridge with a syringe (maybe because the cartridge holes are placed on the front and not on the top like in the video?).
Do you think I should continue to do head cleaning?
Did you pass the step I can’t?
Thanks a lot for your help.

While Piezoflush is designed to help to clear clogs, it is also designed to help desolve the ink BUT it has to be allowed to do so. Repeated head cleaning without letting the flush do it’s job might harm the print head. My suggestion would be to let the printer, with the PF in the lines, just set for 24 to 48 hours, then do one additional cleaning followed by a nozzle check to check on the see if that helps . if it does, then allow it to set for an additional 24 to 48 hours. Do this incrementally and not all at once. Time is your ally.

Thank you for your reply. I will do as you advise. The PF has been installed for a good week. I did two cleaning sessions. There are still two channels where PF does not arrive at all. In almost all the others, not all the “dashes” are present on the image. I could send you a photo of the result, but I don’t think it is possible on the forum.