So my computer updated to Windows 10 without my permission and it has impacted everything. The worst is my Lightroom catalog was wiped. It shows up in a folder on my computer, but every time I try to import (open catalog) it gives me this message. My old catalog was Lightroom 5 and the version on my computer now is Lightroom 5 as well, so I don't understand what is happening. But I was almost finished editing a wedding and now have to completely restart if I can't fix this.
Open the catalog straight from the location where it saved.
Default location for Lightroom catalog is Pictures/Lightroom folder and Open Lightroom 5 Catalog .lrcat file.
Let us know the outcome.
The error message indicates that you may have edited photos in a trial version of LR6 which up-dates a copy of the catalog for use with LR6.
Trying to re-open the up-dated catalog in LR5 will give this message.
You will still have an old 'copy' of the catalog that was used by LR5 if you search for it. It will not contain any of the downloaded images or develop editing done to the LR6 catalog, but it will still open in LR5.