Do you use CDN?
Can you disable all your other plugins except this one. Then carry out a test?
If the above does not work can you delete and remove the plugin by following these steps.
– Disable and delete the plugin from your website.
– FTP into your website and download the .htaccess file to your computer and edit and remove all the code between and including the following tags:
# BEGIN All In One WP Security
# END All In One WP Security
– Log into phpMyAdmin and locate the database for the website you are having problems with. Look for any table entry with the following name aiowps and delete those tables.
There should be 5 tables associated with this plugin:
aiowps_events
aiowps_failed_logins
aiowps_global_meta
aiowps_login_activity
aiowps_login_lockdown
The above will remove this plugin and all traces from your website. Then you can install a fresh new copy. Make sure the captcha is not enabled. Then report back with your results.
Thank you