Internal Server Error – Multisite installation

After updating the .htaccess file, I get the following error when visiting my site:

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.
…
More information about this error may be available in the server log.
Apache/1.3.42 Server at plansonintl.com Port 80

code on .htaccess file:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
# Media Vault Rewrite Rules
RewriteRule ^wp-content/uploads(?:/sites/[0-9]+)?(/_mediavault/.*\.\w+)$ index.php?mgjp_mv_file=$1 [QSA,L]
RewriteCond %{QUERY_STRING} ^(?:.*&)?mgjp_mv_download=safeforce(?:&.*)?$
RewriteRule ^wp-content/uploads(?:/sites/[0-9]+)?(/.*\.\w+)$ index.php?mgjp_mv_file=$1 [QSA,L]
# Media Vault Rewrite Rules End

# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

https://ww.wp.xz.cn/plugins/media-vault/