failure to heat nozzle and bed

Hello. I am brand new to a 3D printer. Printed the cat twice, but can’t print anything else. Did the preheat, leveling of the bed, adding the filament which is 1.75mm. From the SD card, choose a 3 star pointer, when you hit print, then quickly pause, the nozzle and print bed shows “0” for heat. What did I do wrong? So, added some heat measurements, but half way through, bed and nozzle cools down and kicks the star off the bed into the floor. Suggestions?