The plastic piece that pushes the latch to open the door is broken. I have had the same thing happen. The piece has a plastic post that’s about a 1/4” in diameter and this pin/post pushes the latch up to clear the holes to open the door. This piece seems surprisingly weak comparing to the force it takes to overcome the spring load. You have to take the main covering apart to get to the part. You will need to replace the part. On the same plastic is an electrical switch mounted that gets activated when the door is open and stops the glass dish rotating inside. Because the switch doesn’t get triggered the dish continues to spin even when the microwave is not on.