1. Once you imported the image, 'embed' it first, then go to 'Layers', select name <image> in the same layer by collapsing the layer name arrow down, then try the envelope distort, it will work. (This option will provide an accurate result for envelope distort than making clipping mask) *see attached
2. If you are clipping masked the images already, then embed it by going in the isolation mode, them exit isolation, and Distort it ( the difference between the two methods are attached)
So I suggest you crop the image and do the distortion than clipping mask it.