sensor bins

I bought the sensor bins from Groupon just over a month ago and only started using it less than a month now and it is already not working. The lid is supposed to sense and open on it's own and it is no longer working like that. It was fine in the morning and last night when I got home it stopped working and I put brand new 4 d batteries in it so it is not the batteries. the light still comes on and it makes the noise of the lid opening but only it is not opening.