A colleague helped me with editing in LR. I have LR 5 and colleague LR5, this is however not the problem. We worked on colleague's PC. Once I imported the catalogue created back onto my PC, the conversion from LR5 to LR6 was no problem. The problem is, I cannot get all my photographs back. LR keeps finding the one catalogue I've imported.
EDIT [moved to correct product forum – moderator]
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I think there are two separate issues:
-Converting the LR5 catalog to LR6 catalog
-Merging with your master catalog
I think you will have to export again the new catalog (now in LR6 format)
Then choose your master catalog from the list (File >> Open Recent) and when that re-opens import the newly exported catalog with negative files.
The problem is, I cannot get all my photographs back. LR keeps finding the one catalogue I've imported.
If there are other catalogs that you want to find and import into LR 6, then you have to navigate to the location of those other catalogs using the dialog box that appears when you select File->Import from Another Catalog. If you don't know what folder to look in for those other catalogs, then use your operating system's search feature to search for all files whose name ends with LRCAT.