You should remove all Ultimate Seo Url htaccess rules

Your htaccess should look like this

#### BOF SSU
Options +FollowSymLinks -MultiViews
RewriteEngine On
# Make sure to change "zencart" to the subfolder you install ZC. If you use root folder, change to: RewriteBase /
RewriteBase /

# Deny access from .htaccess
RewriteRule ^\.htaccess$ - [F]

RewriteCond %{SCRIPT_FILENAME} !-f
RewriteCond %{SCRIPT_FILENAME} !-d
#RewriteRule ^(.*) index.php?/$1 [E=VAR1:$1,QSA,L]
RewriteRule ^(.+) index.php?/$1 [E=VAR1:$1,QSA,L,PT]
#### EOF SSU