make_grid will create a grid using all samples in the current batch and transform it into an image format.
Based on your code I guess you are seeing an error claiming that the input shape is invalid.
If so, this error is expected since matplotlib expects input arrays in an image formar as [height, width, channels] where the channels dimension might be missing in case of a grayscale image.
Your model output should have the shape [batch_size, channels, height, width] so you would have to index the sample you would like to visualize in the batch dimension and permute the image to the aforementioned channels-last format.