The coffemaker won't brew and showed a descale message. What does that mean?

Scale---or mineral deposits---form from the water you run through your Keurig coffee machine. If not cleaned regularly, the buildup can clog the lines in your machine and ruin the heating element. The manufacturer recommends you descale Keurig coffee makers once every six months for normal water conditions and once every three months if you live in an area with hard water
1.Unplug the coffee machine and remove the cup.
2.Turn the coffee machine upside down over the sink in order to fully drain it of water. Be careful of the plug and avoid getting it wet.
3.Pour undiluted white vinegar into the reservoir up to the top edge of the viewing window.
4.Place a ceramic cup under the machine, plug it in and press "Brew" for a large cup. Pour the cups of vinegar into the sink and repeat the process until the reservoir is empty.
5.Remove the final cup of vinegar and empty it. Fill the coffee maker with clean water and allow it to sit for four hours, remaining on.
6.Unplug the machine and dump the water into the sink.
7.Fill up the reservoir with fresh, clean water and plug it in. Place the ceramic cup back on the drip tray and run multiple brews in order to rinse the machine of any remaining vinegar residue