I upgraded to 15.0 and a collection set disappeared.

[thomasd78609105]

I had been working on the collection set up until a few days ago, had exited lightroom then had used it for an unrelated collection. I then upgraded to 15.0 and the entire collection set disappeared. Does anyone have any hints on how I might recover it?

thank you

[dj_paige]

I am skeptical that the upgrade process would lose one collection set but nothing else.

However, first you have to find the collection set in earlier catalogs. Then you should be able to transfer the individual collections to the new catalog. In the old catalog right-click on a collection and selecting Export this Collection as a Catalog, then import this catalog into your new catalog.

[KR Seals]

Do you have multiple Lightroom Classic V 14.x catalogs? If so, V 15 might have updated an older one where the collection was not present.

[dj_paige]

I think @KR Seals has a very good thought on this matter. What he said is more likely the reason than LrC upgrade lost one collection set out of the entire catalog.