How to fix issue with magento 2 cache ( images not visible in frontend in developer mode, images not showing when new product created using duplicate, images visible when resize:cache command run only )?

When you don't see images on a product page after duplicating an item or creating a new one, you may have a problem with the .htaccess file in the /pub/media folder

To fix the situation you need to restore the correct state of this file.

The most important lines to solve this problem are the following:

## rewrite everything else to get.php
    RewriteRule .* ../get.php [L]

If you don't understand how and where to insert it, just download all your version files from the archive.

And take from the downloaded zip archive file /pub/media/.htaccess and replace with it the file on your server at the path /pub/media

Full explanation of this issue is here

It's done!