Someone gave me an older Pro4000 printer with refillable carts that I’ve been using with no problems until recently. I went to use the printer after a few weeks away and 3 colors wouldn’t read. After being unable to get these to work (all 3) I finally ordered 3 new chips. After installing the chips, I still couldn’t get those three to read. So I give up for a while. A week later I try again. Voila! All carts reading… except… now it says “No Mnt Tnk”. I tried resetting. A different maintenance tank - nothing.