The shortest answer would be: Please go to WordPress Dashboard > Security > Settings > Advanced > System Tweaks and uncheck “Disable PHP in Plugins”. Then click Save button.
Wise Chat Pro executes PHP files directly in /wp-content/plugins/wise-chat-pro/src/endpoints/ultra directory on your server. It is done strictly for performance because the standard admin-ajax.php endpoint is too slow and we were forced to implement a much lightweight code. Some security plugins treat this as a security matter, but do not worry. It is 100% safe.
A much less recommended option is switching the chat’s engine to the default: WordPress Dashboard -> Settings -> Wise Chat Pro Settings -> AJAX Engine and set it to Default. Note that this is not recommended as it may seriously slow down your site.
Advanced option
Please edit .htaccess file and locate iTheme Security entry. Then please add the bold line exactly as this:
# Disable PHP in Plugins - Security > Settings > System Tweaks > PHP in Plugins
RewriteCond %{REQUEST_URI} !/wp\-content/plugins/wise-chat-pro/.*$ [NC]
RewriteRule ^wp\-content/plugins/.*\.(?:php[1-7]?|pht|phtml?|phps)\.?$ - [NC,F,L]This will add Wise Chat Pro as an exception to “Disable PHP in Plugins” option in iThemes Security.