Hello,
Thank you for correcting the login details. I could now log in to your site, however, I could not find what is causing the error. This error message is typical to caching issues, but I can see that the cache plugin is disabled on your site. There might still be some kind of caching in place, in a mu-plugin or on the server-level, you may want to check up on that with your hosting provider.
The error can also be explained by another plugin running a query and not completing it or clearing it correctly, so the mysql connection is left in an inconsistent state and Rank Math cannot process its own query.
As a developer myself, I can tell that the function in the referenced file cannot be responsible for this error on its own, there must some other unknown factor on your site/server. The error basically says that we cannot call the WP core function delete_option() on the shutdown hook, which doesn’t make much sense, normally there shouldn’t be such limitation. Besides, this is working correctly on hundreds of thousands of sites. Of course I know that this doesn’t solve your issue, I’m just stating that the issue is most probably not in Rank Math’s code.
There are a few things we can try, to troubleshoot this issue:
1. If you haven’t already, try using the Troubleshooting Mode in the Health Check plugin. The Health Check plugin is a free official tool from the wp.org plugins team, and its Troubleshooting Mode lets you as an admin test a plugin by itself, without the other plugins and with a default theme, to see if the error is related to a conflicting plugin/theme. Visitors will still see the original site without any changes while you use the Troubleshooting Mode.
2. We can try changing the priority level of our callback function on the shutdown hook, as the issue seems to be related to that. To do that, please open the plugin file seo-by-rank-math/vendor/mythemeshop/wordpress-helpers/src/class-notification-center.php and find this line in it (line number 48):
add_action( 'shutdown', array( $this, 'update_storage' ) );
Add , -10 to change the priority (from the default 10) and make our callback run before anything else:
add_action( 'shutdown', array( $this, 'update_storage' ), -10 );
3. We can also try putting the problematic function on another hook. To do this, edit the same line I mentioned above. Change shutdown to wp_after_admin_bar_render:
add_action( 'wp_after_admin_bar_render', array( $this, 'update_storage' ) );
4. We can try deleting one line in the code, to see if that’s the only place where it fails. For this, you need to find and delete one line in the same file seo-by-rank-math/vendor/mythemeshop/wordpress-helpers/src/class-notification-center.php, line number 156:
delete_option( $this->storage_key );
Please try the above points and let us know the results, that may help us find a way to prevent this error from occurring again. Thank you.
