I am trying to run the wp-cron.php manually by calling it that way:
http://mysite.com/wp-cron.php?doing_wp_cron
Disabling the auto cron function with :
define('DISABLE_WP_CRON', TRUE);
produces the same error.
What could be the issue?
Getting Error “invalid secret string” by running wp-cron.php manually
If you’re launching wp-cron manually you don’t need the “doing_wp_cron” parameter. The fact that you have it and haven’t given it a value is very likely to be what’s causing your error.
Edit wp-config.php and add the secret key. A good spot is right after the Authentication Unique Keys and Salts. Please be sure to update the secret to be your own.
Then you can run
Where the part after the & is the secret key which you created with the define statement in wp-config.php
For others with this issue, make sure you don’t have a plugin like WP-Cron Control enabled (source).