If the product images are missing after an upgrade for example, the following command (executed in the root of your Magento 2 shop) might help:
php magento catalog:images:resize
Note: Depending on the mumber of products, that might run some time.
Product images missing on category page
You want or need help implementing this solution? Maybe you did not find what you were looking for? Contact me and I will assist you with whatever Magento problem troubles you!