Thumbnails does not display in media library for a multisite setup

I am using wordpress 4.3.1, and thumbnails does not display in media library of subsite, rest all images works perfectly fine even in mainsite. Media library also works fine in main library. Even grid layout does not work and just keeps loading infinitely. I searched everywhere and wasted a whole day and still not able to arrive at a solution 🙁 my .htaccess file

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*.php)$ $1 [L]
RewriteRule . index.php [L]
</IfModule>
# END WordPress