SEF Advance installed but not active

Hi, fist, excuse me for my english, i'm french.

I have installed SED Advance, replaced olf .htaccess file, and activate SED Advance and Joomla SEF, but sed advance do not work !!

For test sef advance, i have changed space to "_" and unique item to "yes", and now i'm sure : sef advance do not change any url !

could you help me please ??

thanks

Dany