wordpress multisite not working on Localhost

I’ve installed wordpress in multisite mode on my localhost. I am using WAMP server on windows 10.

The parent site works well and can be accessed. However when I try to go to the sub sites It says the URL was not found on the server. Both for the sites as well as their backends.

I have followed the network setup instructions as specified by wordpress.

I think it’s an issue with mod_rewrite, how ever in my httpd.conf when I uncomment

#LoadModule rewrite_module modules/mod_rewrite.so

I get an internal server error

My htaccess file is

# BEGIN WordPress
<IfModule mod_rewrite.c>

RewriteEngine On
RewriteBase sandbox/mainsite/
RewriteRule ^index.php$ - [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).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*.php)$ $2 [L]
RewriteRule . index.php [L]
</IfModule>

# END WordPress

Another curious thing is that when I change the permalinks in wordpress to custom structure and hit save, it does not get saved and reverts to the previous setting.

Any Ideas?