magento1.9.3 – Magento 1.9 Recently viewed products do not show up

getLayout () -> createBlock (& ​​# 39; reports / product_viewed & # 39;) -> setTemplate (& # 39; reports / product_viewed.phtml & # 39;) -> toHtml (); ?>

This code supposes to leave the Recently viewed products on the category page or the product page (by inserting the code in .phtml files). and it has always worked for me on my Magento sites.

However, I found that for a site (Magento 1.9.3.3), this code did not work at all. and for this site, the widget show recently viewed product does not work either.

Any ideas that can cause "recently viewed products" do not work?