Gallery thumbnails are not generated

Question

We need to import a lot of products from different vendors (about 30000 products). For some products the thumbnails are not generated in the front end.

I tried clearing the cache, clearing static content, running deploy, reindexing, reimporting, everything.

Any ideas why this is happening?

Running Magento 2.3.1

Answer 1

Turns out it was an issue with the template. The template creators fixed the problem.