attributesForFaceting configuration (facets) is handled by our plugin for Shopify: if you edit these configuration directly on your Algolia Dashboard, those will be overridden when you run a reindexing operation.
You can find more information about this on the following FAQ: Which settings are handled by the Shopify integration and which by the Algolia dashboard?
When configuring facets, all changes should be made in the "Facets" configuration section of the Algolia Shopify app, (not the Algolia Dashboard).
In the Algolia Shopify app go to:
Search Options > InstantSearch > Customize > Facets
This will show all of the default facets, along with any custom facets that have been added via Named Tags or Metafields. To add these facets you need to click on the + icon and save the configuration.
If you don't find your facets on the Inactive list, please refer to this guide article: Why are some of my facets not showing on the Search options of the plugin?