SOLVED:
This is issue was solved by correctly flushing rewrite rules:
global $wp_rewrite;
$wp_rewrite->init(); //important...
$wp_rewrite->flush_rules();
SOLVED:
This is issue was solved by correctly flushing rewrite rules:
global $wp_rewrite;
$wp_rewrite->init(); //important...
$wp_rewrite->flush_rules();