Let me save you 5 minutes of precious internet or www.hp.com searching.
If you put a toner cartridge in the printer and turned it on and had the light show up, but the printer is printing normally, then you probably used a toner cartridge from a third-party vendor and not from HP. Hewlett Packard original cartridges have a circuit on them that tells the printer that the toner has been installed…3rd Party cartridges lack that circuit.
 So don’t worry, just print away.
