Hello @TK-1
Welcome to Shopify Community.
Did you checked that your the Ella theme you installed is a 2.0 theme or not ?
If it is a 2.0 theme than the filters will work with it so you can contact the theme developer to check the issue.
If it is not a 2.0 theme than you need to upgrade to a 2.0 theme and you will need a developer to setup the filter code in the Ella theme.
Thanks