If you have access to server via SSH then do Check 1 and 2
Check 1: if you have access to httpd.conf then check for
LoadModule rewrite_module modules/mod_rewrite.so
and uncomment this line.
Check 2: if you have access to httpd.conf then check for
FIND SECTION BEGINNING
Options Indexes FollowSymLinks
Allow from all
SAVE FILE AND THEN
# service httpd restart
Check 3: Go into your .htaccess file and uncomment
# RewriteBase / [ It is line 101 in my .htaccess file.]
or once your hosting service enable this mod_rewrite.
In Drupal check for this path
admin/settings/clean-urls and choose to enable clean-urls here.