I don’t get any error message. Just go back to settings screen.
But now I’ve activated WP_DEBUG = true and I’ve got the following after enable recurrence:
Deprecated: Function eregi() is deprecated in /public_html/wp-content/plugins/optimize-db/optimize-db.php on line 76
Notice: wp_deregister_script was called incorrectly. Scripts and styles should not be registered or enqueued until the wp_enqueue_scripts, admin_enqueue_scripts, or login_enqueue_scripts hooks. Please see Debugging in WordPress for more information. (This message was added in version 3.3.) in public_html/wp-includes/functions.php on line 3245
Notice: wp_deregister_script was called incorrectly. Do not deregister the jquery script in the administration area. To target the frontend theme, use the wp_enqueue_scripts hook. Please see Debugging in WordPress for more information. (This message was added in version 3.6.) in /public_html/wp-includes/functions.php on line 3245
Notice: has_cap was called with an argument that is deprecated since version 2.0! Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead. in /public_html/wp-includes/functions.php on line 3193
Warning: Cannot modify header information – headers already sent by (output started at public_html/wp-content/plugins/optimize-db/optimize-db.php:76) in public_html/wp-content/plugins/events-manager/classes/em-notices.php on line 40
Warning: Cannot modify header information – headers already sent by (output started at public_html/wp-content/plugins/optimize-db/optimize-db.php:76) in /public_html/wp-includes/pluggable.php on line 1121