Sometimes when you run the Elevate commands in Site Data Prep they don’t always work, below you will find a number of things that I have found that may help you
If you have a linework cross and elevation labels that you want to create points at the X location and elevate with the text values, I have found that e.g. Left Middle justified text will fail but right middle justified text will work.
If you have contours and contour labels, if there are multiple labels on each contour, only select one label per contour. If you select more than one label on each contour, it seems to fail to work on those contours.