I am the webmaster of the German WordPress website http://www.kunstplaza.de.
Recently, I have noticed that there are no items in the RSS feed, although there should be some as I am posting new articles on a regular basis.
The Feed URL is: http://www.kunstplaza.de/feed/
As far as I remember, this feed did work in the past. I have already deactivated all plugins and themes (one by one) and tried to retrieve the feed after that. Unfortunately, this did not have an effect. Only when I rename the "plugins"-folder, the feed starts to show up.
In the error log of my hosting provider I have found this line quite some times:
[error] You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ']posts.ID NOT IN ( ) ORDER BY wp_posts.post_date DESC' at line 1 f\xc3\xbcr Abfrage SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND (wp_posts.ID = '296') AND wp_posts.post_type = 'page' AND $wpdb-]posts.ID NOT IN ( ) ORDER BY wp_posts.post_date DESC von require('wp-blog-header.php'), wp, WP-]main, WP-]query_posts, WP_Query-]query, WP_Query-]get_posts, W3_Db-]query, W3_DbCache-]query, W3_DbCallUnderlying-]query, W3_Db-]query, W3_DbProcessor-]query, W3_Db-]default_query
I guess, this is the error that blocks the RSS feed from working in a correct way. It seems as if the W3Cache Plugin is causing this issue. I have already deleted the whole plugin and reinstalled it from scratch. This did not solve the issue. I am using this plugin on other sites with the same configuration without having any problems.
I guess, the database needs to be repaired somehow. Unfortunately, as I am not a programmer, I do not have an idea of where to start or which db tables could be involved.
Does somebody of you have a clue? What could be a potential source of this issue?
Thanks a lot for your feedback!