The repair center. Yes you can try home remedies like cleaner the cartridge holder's contacts but these things do fail after a time and then it's off to the repair center where they replace the parts that failed.
But here's the next problem. Repair fees may exceed the cost of a new printer.
I have a Brother Printer MFC-845cw. One cartilage went empty and when I replaced it the printer still shows empty. I bought another cartilage and same prolem. I have removed and inserted more than 25 times. How do I remedy this problem