Thank you for using the Support Forum. First please see the article Find the serial number for 2 ways to find your serial number. As for the light please remove the toner cartridge. Power off the machine. Insert the new toner cartridge and make sure it slides all the way into the printer. Turn the machine back on. If the light still blinks, remove the cartridge and lightly shake it from side to side 5 to 6 times and reinstall. If that does not take care of it you can either try another cartridge or call the support centre back for additional assistance.