Filters dropdown not visible in posts list

Hello,
I wanted to make the dropdown filter (latest,popular,title) visible in posts list here https://accademiainfinita.it/forum/index

but I see this CSS

<select data-index-sort-filter="" style="display: none;">

I don't know if someone tweaked the file, problem is I don't have any custom files in my template html folder, and I can't find the file in the component folder to look into it

could you tell me where to find the file that contains the code for this filters dropdown? I am using the Wireframe template.

Thank you