Disregard my previous correction of the .htaccess file. Instead of adding "S=" in the 1st row, U should have your .htaccess file look like this:
Notice there is a new RewriteRule added at the end. This should work 100%. I will let u know if there is anything wrong.
Hey guys I had the same problem and found the solution today. The .htaccess file is slightly incorrect. This is the default that was given to us:
Now here is the correct version:
Look at the 1st rewrite rule on the corrected version and u should see "S=". This is what is needed to make all of your links able to be URL Friendly when u choose that option in PrestaShop. I hope this works for u as it did for me. I went crazy for months trying to figure it out.