Some possibilities:
Extents problem. What I mean by that is that the image is being displayed but the Full Extent command is taking you to a zoom level which is too far out (in your case you have 1 : 1,238,063). Can you zoom to the area where you know that the image should be displayed at a reasonable resolution?
Projection (spatial reference) problem. Is the coordinate system associated with the image correct?
Image service creation problem. When you created the image service did you take the steps needed to remove all the warnings, e.g. generate statistics, overview, pyramids, etc.? You did not describe the steps that you followed to create the image service.