If you are using the Yoast SEO plugin with FacetWP, do not enable the “Remove unregistered URL parameters” setting:

Leave Yoast SEO's 'Remove unregistered URL parameters' disabled.
Leave Yoast SEO’s “Remove unregistered URL parameters” disabled.

This setting is located under:

Yoast SEO > Settings > Advanced > Crawl optimization > Advanced: URL cleanup > Remove unregistered URL parameters

If you enable this setting, Yoast SEO will strip FacetWP’s URL parameters and create 301 redirects when the page is reloaded with AJAX when filtering, which prevents facets from working.

See also