Permalinks Not Working

Permalinks are not working like they should. They were working on older versions…but seems that are not working on the new 2.5.1 version.

I’ve set Permalink “/%category%/%postname%” and the links should be like “https://sitename.com/category_name/postname” but it isn’t…it looks like “https://sitename.com/category/category_name/postname”.

I’ve selected the default permalinks and seems they are not changing.

What can i do ?

Thank you !