Darcy asked me to get involved with the problem you are having.
As I understand it, the original problem was that ink cartridges were being rejected by a 5500. The ink cartridges were replaced with new OEM cartridges and the problem persisted. We sent a refurb. Ink tube system that did not help followed by a new OEM ink system. You also installed a used known good ink cartridge in the failing slot with no change in symptoms.
The problem is that the ink cartridge is not communicating with the electronics module for some reason. You have done all the logical things so far with the ink cartridges and ink tube systems. The problem must be upstream from the ink tube system. The possible failing components from here are: the cable connecting the ink tube system with the ink tube system controller on the emod, the ink tube controller board, or the cable that connects the ink tube controller with the main logic board. Since none of these parts are expensive, I suggest replacing them together to get the machine running as soon as possible.
If your customer replaced the soft air pressure tubing, there will likely be air leaks. It is not possible to clearly view the tube connections at the cartridge valve assemblies without removing the valve assemblies. That will prevent the system from pressurizing and moving ink through the tubes. I just want you to be aware there may now be a secondary problem ahead.
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