PSE 15 Photomerge panorama failure. Works with 2 files not 3 or more.

When I set 3 files to become a pano, all steps appear to work, each file processed, layers made, then image of the pano disappeares. Working with 2 files, same process however the panho stayi in the photo bin. Then I can work with it in expert mode. Is there a file size limit which mayh cause this. Should not there be an error message?