I just had the same problem. Started a thread 3880 says NO CARTRDIGE, but you can reply here. I did what you said above, initially with no success. But I ejected and then pushed in all the carts several times until it finally took. I started from the left and once I pushed in the yellow cart, LCD said “cartridge door open, close door”. What you’re saying above is that all carts can indicate “no cartridge” even if only one cart isn’t making proper contact. Is there any way of finding out which one it is? In my case I suspect it was the yellow cart but can’t know for sure. This isn’t the first time I’ve removed carts. A while back I removed several carts to top off with ink, but didn’t have a problem. Now that I’m aware of this, a better procedure in the future would be to only remove one cart at a time. After it’s reinstalled, make sure the LCD says it’s OK before taking out another cart. This way if removing a cart causes this problem, I can easily identify which cart it is and deal with that cart.