If you are not able to delete plugins or themes on your child sites that are hosted with the WP Engine via your MainWP Dashboard, it is due to the WP Engine platform configuration.
Solution
To fix this, please contact the WP Engine Support Department and ask your support agent to add an Nginx rule that allows the MainWP User-Agent to access your child site. If you have multiple child sites on WP Engine, the Nginx rule has to be added for each child site.
MainWP User-Agent
“Mozilla/5.0 (compatible; MainWP/3.5; +http://mainwp.com)”
The version number in bold changes with each release.
Example of the Nginx Rule:
Nginx before-in-location
set $mainwp_ua 0;
if ($http_user_agent ~* MainWP){
set $mainwp_ua 1;
}
set $mainwp_location 0;
if ( $uri ~* "^/(wp-cron\.php|wp-admin/admin-ajax\.php)" ){
set $mainwp_location 1;
}
set $both_mainwp_vars "$mainwp_ua:$mainwp_location";
if ($both_mainwp_vars = "1:1"){
set $is_trusted 1;
proxy_pass http://localhost:6788;
}