NO REAR Defrost, need major help

Hello to everyone who reads this message, I have a 1996 Pontiac Sunfire,

I have no rear defrost. I push the button, the light comes on with a click, but the window does not defog. There is power going back there, and across the window. It is just simply not defogging! I will welcome any and all information on how to get this problem fixed,

thank you to all