Today, i got several messages on my inbox asked about the same thing: why the featured image option is gone from my dashboard?
Suddenly, the featured image option is no longer available when they were editing/create a new post and photograph.
When i try this theme (Lensa) on my server and also localhost, there is no problem on it. But, my friend from Iran, Yamesh gave me his FTP and WP-Admin account information to check the problem.
To fix this problem is very simple though, just add this code at a file named functions.php:
add_theme_support( 'post-thumbnails' );
Put those code at the very end of the file before you find this code: ?> and your featured image will be back.