404 error when try open image from thumbnail

looks like you are having a problem with your rewrite Engine

in the .htaccess file.

take a look at it before and after setting your permalink structure and see if there is any change.

It may need to be updated manually

Well… It`s all ok with .htaccess file.
This code in file after setting permalinks /category/postname/ mode.

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

And all work fine, but not thumbnails…

do you have a link to the site ?

Does anybody no how to fix this? I have seen ton’s of people ask about this, I’m having the same problem.

Ok, guys, it`s a bug!
https://codex.www.ads-software.com/User:Lolrus/Using_Attachments#Troubles

see Attachment page not found (404)