Multisite Problem after upgraded to WordPress

https://www.example.com/blog/site1 — theme, posts are not showing up
https://www.example.com/blog/site1/wp-admin –throwing me up continuous redirect errors on google chrome.

What shows up for /blog/site1/ ? Content without style?

Its shows up my
https://www.example.com/blog/ ‘s NOT FOUND page

What’s in your .htaccess?

before upgrade it was

RewriteEngine On
RewriteBase /blog/
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).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]

now after upgrade it is like

RewriteEngine On
RewriteBase /blog/
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).*) blog/$2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ blog/$2 [L]
RewriteRule . index.php [L]

Change it back ??

Out of curiosity, why did it change?

I removed and updated few plugins,
I also tried deleting a site and then creating a new one

Till then it was all fine. As soon as I created a new one the wordpress started acting wired. ??

Did you change the .htaccess back?