Multisite new site not found, error 404

Hello everybody,

I tried to convert my single-site to multi-site based on some instructions, I did everything and compare my settings to 3 different instructions and youtube videos. Everything seems to be correct but when I try to see my sites inside my network, it is not possible!

Somewhere in the middle of setting up the network, there was a message saying that since you have an up and running wordpress with content and users, you can not use directories and you must select sub-domains.

My website (the main original one) works fine, but when I add another site, the only thing I can see is the title under My sites and the link to dashboard etc. but none of the links work.

The interesting thing is I made two sites, and I see two different errors when I try to check them out!
The first one ends up to “This webpage is not available”, but the other one goes to a 404 error!

This is my .htaccess:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^(.*\.php)$ $1 [L]
RewriteRule . index.php [L]

Can anybody tell me what to do now?

Thanks,
Nima