HTTP Error 406 always on site?

Hello WordPress community,

I am getting http 406 error in my website when ever I tried to change something in my site. it looks similar like this below line

This page isn’t working
If the problem continues, contact the site owner.
HTTP ERROR 406

I tried this in htaccess but the result is same .

IfModule mod_security.c
SecFilterEngine Off
SecFilterScanPOST Off
/IfModule

# BEGIN WordPress
# The directives (lines) between BEGIN WordPress and END WordPress are
# dynamically generated, and should only be modified via WordPress filters.
# Any changes to the directives between these markers will be overwritten.
IfModule mod_rewrite.c
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
/IfModule

# END WordPress

I have also disabled the mod security from the cpanel but the result is same.

Can any one help me with this issue ?