Upgrade PhotoStore version 2 or 3 to version 4At this time it is not possible to upgrade version 2 or 3 to version 4. If you wish to use version 4 it would have to be a completely new install to where you would have to reupload all the photos, create categories, etc.. It will be a brand new install with no photos moved from previous versions, you will have to reupload all your photos, categories, etc.. It is impossible to move photos and other data from version 2 or 3 to version 4.
Due to version 4 being written from the ground up, it doesn't share anything in common with the older PhotoStore versions. That is the main reason why it is impossible to upgrade to this version from an older version of the PhotoStore.