Due to some firmware updates with some Lexmark printers, some aftermarket Lexmark 100 / 100xl ink cartridges may not be recognized by the printer (printer will either not recognize the cartridge, or recognize it with low or no ink). The following procedure has been found to overide this issue in almost all cases:

1) Expose the chip (it is beneath the label on the top of the cartridge, as shown in Figure 1 below)
2) Between the letters "A" and "B", there is some black carbon coating on the chip. Using a sharp object (be careful), scrape away at the black coating, to result in Figure 2.