Cant access subsites dashboards

I have a multisite installation and all of a sudden I cant access their dashboards and also when I visit the site the site is broken the themes configuration neither working. I contacted my host and they said:
There was an incorrect .htaccess rewrite rules defined in your WordPress Multisite installation. However, I’ve updated the .htaccess file with the required rules and you should now be able to access both website and Dashbaord

But now they have messed up my main website. I changed again the htaccess rules to:

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).*) $1 [L]
RewriteRule ^(.*\.php)$ wp/$1 [L]
RewriteRule . index.php [L]

But I keep receiving this message Error establishing a database connection

What can be happening?
Thanks