I have migrated Magento 18.104.22.168 to Magento 2.1.6 with the help on the Data Migration Tool.
I moved manually the media files following the documentation.
The problem is that in the backend product list I only see the Magento thumbnail placeholder (gray icon). If I enter the product I can see the images attached.
I can only see the thumbnail if I edit the product and hit save. Then the thumbnail is shown in the list.
But I don't want to do this for 3k+ products.
Do you know what could cause this issue and how I can solve it?
Thanks very much,