Due to layered navigation block disabling robots by default…
Hi, the problem comes from the “Layered navigation block” module. After the update to v2.2.1 something has changed.
To Fix the problem for Prestashop 1.6 go to Modules and Services >> Layered navigation block >> Configure
Scroll down to the CONFIGURATION section and set to YES the “Allow indexing robots….”
This action will change the metatags for all category pages to “indexed, follow”