You probably just need a new button. If you look at the wires on the defroster, you may find one that's broken. You can buy a repair kit for these at most auto parts stores. Just follow the directions. Also you need to check your fuse box and if that doesn't work, you've got a bad wire somewhere.
Check that the wire on the rear defroster is connected to the defroster. If broken off repair it.
There is a repair kit available to repair the grid. A test light will find the break in the grid.
AUTOZONE.COM click REPAIR INFO, then click, REPAIR GUIDES
go to auto parts store and purchase a haynes repair manual
You need check it. Very often it gets scratched and as a result damaged. If it's damaged even in one place it will not work. If it's the case you can repair it using a special defroster repair kit which you can get from Advance Auto parts. Check the fuse too.
You call an Auto Glass repair shop. This is not a DIY job. Your insurance will almost always pay for this repair.
Check the fuse first. Then check, with a volt meter, to see if there is 12 volts D.C. to the defroster at the place where it is plugged in. If you have voltage then look at the defroster heat strips and check for a break somewhere. There are repair kits for a broken power strip. If the fuse is good and you have no voltage, check the wiring, switch, & relay.
Find an armor vendor and press the repair button in the transaction window.
kick it
you can hold the menu button along with middle button hold it for 10 seconds
The lines (grid) on the rear windshield are scratched or cut. You can use a repair kit from the auto parts store or some silver solder to repair the breaks in the grid.
Muscle tissues