Upgrading brand page

I’m trying to load filters for brand page and the brand page with products is working fine. But loading filters for brand page products is not working fine.
The reason is
var productCatalogData = _routeRequestInfoAccessor.RouteRequestInfo?.Data as ProductPageData;
On the above line of SubNavigationViewModelBuilder, Data is null. What could be the issue, here?

Litium version: 7

Not sure what you upgrading from and exactly what you do. I tried on our demo-site to setup a brand page for the products (it is working today and will be removed during the nightly cleanup job) and there the filtering is working. Maybe you can compare the code you have in accelerator 7 to the brand page you have in your version?