Upgraded from 2.6 "No Data Received" on sub sites (Path setup)

Hi, I have been banging my head over this issue for the last week, searching forum posts, asking friends etc.. But I think I’m at a roadblock because I’ve tried just about every solution that I’ve found while googling. My problem has two parts: 1. The main site works fine, but if you go into a sub site, the browser says “No Data Received” and 2. If go to the sub-site’s dashboard it forces a logout. You can login normally, just not as a user of a sub-site.

Here is an example of the page that is getting the "No Data Received" error: https://tcgdev.net/zachbunn

Just for clarity, there is a sub blog named ‘zachbunn’.

If anyone could help me debug this issue, you would be a lifesaver. I would even pay via paypal since this is for an important client, and it’s overdue.

Would be happy to provide logins privately or whatever else you need.

Skype name is codyodell if you want to chat.

Thanks!

EDIT: In firefox, the error says “The connection was reset”. In Safari it say “The server unexpectedly dropped the connection”

Here is my htaccess file and part of my config file:

Options +FollowSymLinks
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).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

define('WP_DEBUG', false);
define('WP_DEBUG_LOG', true);

$base = '/';

define('MULTISITE', true);
define('WP_ALLOW_MULTISITE', true);
define('SUBDOMAIN_INSTALL', false);
define('DOMAIN_CURRENT_SITE', 'tcgdev.net');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);

define('ADMIN_COOKIE_PATH', '/');
define('COOKIE_DOMAIN', 'tcgdev.net');
define('COOKIEPATH', '/');
define('SITECOOKIEPATH', '/');