Product thumbnails not showing and slider not working

Hi,

Amazing plugin.
However, when activated, the gallery is not shown in all the products with multiple images, only in the newest ones, so that in all the old products neither the thumbnails are shown nor the slider works, so the client can only see the main photo of the product.

To get it to work properly on old products, we need to edit each product and save it unchanged, which is unfeasible because we have about 2,500 of them.

Example of old product: /shop/yellow-gold/18k-yellow-gold/18k-oceana-australian-opal-pendant/
New product example: /shop/australian-opals/opal-pendants-necklaces/opal-silver-pendants/light-green-mirror-australian-opal-pendant/

How could we get Product Video Gallery to show up on all products with multiple images?`

The page I need help with: [log in to see the link]