403 error when activating

I migrated my website to another webserver (also domain changed from “something.com/wordpress” to “something.com” if this is important) and now I get a 403 error on the resource “wp-content/plugins/artbees-captcha/generate-captcha.php”. File has the right permissions.

When deactivating Ithemes security the error is gone. After activating it is back again so I asume some configuration prevent the loading of this file (strangly enough because I use exact the same config on my other webserver).

What do I need to configure to prevent this error?