I have a CJ 500 so I have done everything on it my self. On my unit you can easily remove the caps out of the holders to get the tubes out. I could have also just removed the tube from the end that goes to that small rectangle box with the rubber nipples on the other side. This is what moves sideways as the head slide in place and the caps raise up to seal on the heads. Yours may not be the same setup. If you can get at that end you might be able to use a syringe and flush with some cleaning fluid or better yet just use the syringe to blow air through the line to see if it is blocked. If you hear the air or if the syringe has no resistance then the line should be ok and not blocked.
Now I can't tell by the photos in the manuals, for your unit, if it has a similar setup.
If someone can understand what part I mean, and has your printer, they could shed some light.