Why don't the "Prices drop" or "On sale" filters show any results?

The "On sale" filter is used to show only the products for which you display the "On sale!" banner flag (whether or not there is a specific rule created for these products). As soon as there is the flag, the products will appear in this filter. To display the flag, proceed as follows:

Go to the "Pricing" tab of the product and check the "Display the "On sale!" flag on the product page, and on product listings" box:

Save.

The "Prices drop" filter is used to display products for which you have created a specific price rule. If you do not see the products with a specific price rule in this filter, go to the module and click on "Reindex" in the relevant search engine:

To know more about the module search engine reindexing click here.

Under the search engine, click on "Clear cache":

Also clear your browser cache.

Products with a specific price rule should appear in the "Prices drop" filter.