Have you installed the Google Publisher plugin for WordPress?
From their plugin page: “This plugin lets you place AdSense ads using a simple point-and-click UI rather than manually inserting snippets yourself. To insert AdSense ads without the plugin would first involve generating the AdSense snippet and then pasting the Adsense snippet into either the text of the site or directly into the PHP. Google automatically determines potential placements for AdSense ads, suggests an initial ad layout, and allows you to lay out ads on your site.”
Sounds great, except for when it gives you the following error code:
“Unable to apply changes to your site. Sorry we were unable to save your configuration. The request to your server failed with error code 500.“
Activating Google Ads in the Google Publisher plugin for WordPress will show the below image
After that screen, you get the following screen
have you installed the WordPress plugin WordFence? De-activate the plugin and try again to enable ads on your website.
It’s the Web Application Firewall feature that will prevent you from enabling ads. The Web Application Firewall stops you from getting hacked by identifying malicious traffic, blocking attackers before they can access your website. Powered by the Threat Defense Feed, it is automatically updated with new firewall rules that protect you from the latest threats. Even if you are running a vulnerable plugin or theme, Wordfence will protect you from being hacked by blocking attacks based on known and constantly updated attack patterns.
Please contact me if this is not the issue.