Password Issues only when Multisite is activated

Thank you for the question. I should have covered that.
When I initially add activate the Multisite option (by adding the line of code into the wp-config.php) and refresh my page, it works fine and I can see the Network Set option under Tools.

I then go to Step 3 (in the Codex – http://codex.ww.wp.xz.cn/Create_A_Network), which is Installing a Network.

I am asked to add a few more lines of code to wp-config.php. This is how it ends up looking like (just the added lines, the rest of the file was not altered):

/* Multisite */
define( ‘WP_ALLOW_MULTISITE’, true );
define(‘MULTISITE’, true);
define(‘SUBDOMAIN_INSTALL’, false);
define(‘DOMAIN_CURRENT_SITE’, ‘www.andre-costa.com’);
define(‘PATH_CURRENT_SITE’, ‘/’);
define(‘SITE_ID_CURRENT_SITE’, 1);
define(‘BLOG_ID_CURRENT_SITE’, 1);

/* That’s all, stop editing! Happy blogging. */

I am then asked to modify the .htaccess file, which ends up looking like this:

RewriteEngine On
RewriteBase /
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]

Once the .htaccess is modified, my WP install requires me to log in again. I type my username and the password. When I hit the Log In button, the page refreshes and the password box is empty, but there is no error message at all.

Any ideas what I did wrong?
Thank you!