UPDATE: BPS Pro 13+ and BPS 2.0+ versions have a feature called: Setup Wizard AutoFix (AutoWhitelist|AutoSetup|AutoCleanup) that automatically creates plugin and theme whitelist rules and automatically sets up and cleans up caching plugins htaccess code.
The WP Customizer customize.php file is being blocked by the BPS wp-admin htaccess file. Do the steps below to whitelist the customize.php file:
1. Add the customize.php skip/bypass rule below to this wp-admin Custom Code text box: CUSTOM CODE WPADMIN PLUGIN/FILE SKIP RULES
2. Click the Save wp-admin Custom Code button.
3. Go to the Security Modes page and Activate wp-admin Folder BulletProof Mode.
Note: The skip rule must be [S=2] because it will be written to your wp-admin .htaccess file above skip / bypass rule [S=1]. If you have other wp-admin skip/bypass rules already then either combine them or add this skip/bypass rule separately above the other rules and change the skip #. Example: If you already have skip #’s 2 and 3 then this rule would be skip rule #4.
# Flatsome Theme WP Customizer customize.php skip/bypass rule
RewriteCond %{REQUEST_URI} (customize\.php) [NC]
RewriteRule . - [S=2]
.
