From the permalinks I chose the “post name” permalink. I have a plugin that displays, for example, 3 pages. The first page always works, but all other pages are “404 not found”. Only with the default and the numeric permalink the other pages can be displayed.
I talked to the theme developer and he said that it is a problem in my permalinks cause for other theme-users this worked.
My .htaccess looks like
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress
More specific: with “post name” permalink, the address click does not exist, but with numeric permalink, this one works: click (notice that it looks the same)