After migration Featured image src empty for new post

I helped my friend (owner of the blog) to migrate from his provider, Ghandi to a PI.

The domain name is the same.
PHP logs: I activated them a time but saw no error in php_error.log
Nothing relevant in nginx error logs.
The image is well shown “down right” in the editor if I edit the post.
The image URL exist (original) and is accessible: http://www.dagonslair.com/wp-content/uploads/gw2-1.jpg from outside.

The site is working.
Old post (before the migration) are well shown with their own “Featured image”.

But for new post, the img is built “empty” like:
<img alt="img" src="">

I noticed in /var/www/html/wp-content/uploads, for working img there are more sizes:

-rw-r--r--  1 www-data www-data   240944 sept. 15 21:33 guild-wars-2-004-1024x640.jpg
-rwxr-xr-x  1 www-data www-data    11910 sept. 15 21:29 guild-wars-2-004-150x150.jpg
-rwxr-xr-x  1 www-data www-data    26047 sept. 15 21:33 guild-wars-2-004-300x187.jpg
-rw-r--r--  1 www-data www-data    25512 sept. 15 21:36 guild-wars-2-004-300x188.jpg
-rw-r--r--  1 www-data www-data    43050 sept. 15 21:20 guild-wars-2-004-305x305.jpg
-rw-r--r--  1 www-data www-data   142254 sept. 15 21:22 guild-wars-2-004-600x875.jpg
-rw-r--r--  1 www-data www-data   104720 sept. 15 21:33 guild-wars-2-004-817x320.jpg
-rwxr-xr-x  1 www-data www-data     5153 sept. 15 21:21 guild-wars-2-004-92x92.jpg
-rwxr-xr-x  1 www-data www-data   314209 sept. 15 21:35 guild-wars-2-004.jpg

than for failed one:

-rwxr-xr-x  1 www-data www-data   247917 sept. 15 21:31 gw2-1024x575.jpg
-rw-r--r--  1 www-data www-data   358149 sept. 15 21:29 gw2-1024x576.jpg
-rwxr-xr-x  1 www-data www-data    12393 sept. 15 21:30 gw2-150x150.jpg
-rw-r--r--  1 www-data www-data   128759 sept. 20 17:03 gw2-1.jpg

All working IMG have the x320.jpg size. I didn’t find this size in WP setings.
Could you please help me ?

Thanks,
Arfy

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