Trimtint, why don't you purchase a new ink cartridge and use it until you get your problem resolved?
The problem you may be having is that on some Mutohs if you remove and replace an ink cartridge more than 12 times the ink cartridge will shut down. Yes, the only thing you can do for that is replace the smart card.
I had a similar problem when I upgraded the firmware in my valuejet 1204. The upgrade wiped out the smart cards on the ink cartridges. Mutoh sent me new smart cards.
I oulined the location of the old smart cards on the side of the ink cartridges, pulled the old cards off and replaced them with the ones Mutoh sent me. Everything is back to normal now.
I am sorry you are having problems with your Mutoh 1604. I would really like to have a 1604 because it does things the 1204 cannot do.
You may need some training or you may have got a lemon. If your printer is close to new (less than a year old) it should still be under warrenty and you should be able to call Mutoh for a free service call at your site.