Multisite – 404 error

Has installed a multisite at one.com with its own domain and hosting.
With the theme Brooklyn
I have problems with “the other side” of my multisite installation. I can’t even enter the admin panel for the second page “Oops! That page can’t be found.”. It’s at http://www.nicholaswarg.se

I do not understand the help what is written in various forums. They talk about ubuntu and apache on various forums but don’t even know what it is. Have checked wp_config.php and where are all the rows are correct.

What do I do?

—-My.htaccess file—-

# BEGIN WordPress
<IfModule mod_rewrite.c>
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]
</IfModule>

# END WordPress