One of the problems faced by Prestashop users is "Layered Navigation". Layered Navigation gives your users the ability to do a more specific search or better way to sort products and prices to match expectations and improves user experience. Most of the time when Layered Navigation is enabled in the module area, it does not appear on the site. Note that layered navigation appears on category pages in Prestashop.
For the steps in enabling your layered navigation and making it work lets do the following;
1. In your back end go to Preferences >> SEO & Urls >> Turn on Friendly URL (Must be on for layered navigation to work)
2. Go to Modules >> Layered navigation Block >> See the template there and click on Edit >> Select All the Categories and Sub categories where you want Layered navigation >> You can manipulate other filters if you want but not usually necessary >> Hit the SAVE button.
3. On the same Layered Navigation Block >> Rebuild all indexes
5. Check that the Module is hooked to the Left or Right Column where you want it to appear by going to >> Manage hooks on the Module page above.
After all these come back and click on a category with products and see the layered Navigation on the right or left as chosen.
Goodluck, Leave us a comment if it works!