The message that you are getting "File cannot be found" is because the file has been moved from it actual location of the import.
So please go to the Library Module, switch to the Grid View, there you will find an exclamation mark at the top right of the image.
Please click on that exclamation mark and then select the option for "Locate the missing images" and find the images.
Once done reconnecting the images, you should be able to edit them in the Develop Module
Please let us know if it helps.
This did not work. I can't find the images. Other suggestions?