I have a fifty year photograph that it too big for the scanner bed. I have scanned it in two sections as a JPEG file and now seek to merge it in Light Room. The feedback I get is the "LR cannot merge the photo's. Please cancel and review your selections." Any ideas on appropriate procedures to use?
Did you scan with a 30% overlap? I have had the same problem, scanned the photo as 2 separate images and the merge worked perfectly.