Panels not working with page manager?
Panels and Page Manager in Drupal 8 are under heavy development, so probably it's a temporal problem. 

In Drupal 7 Page Manager is a submodule of CTools, but in Drupal 8 is a standalone module. The reason for this is Page Manager tasks (configuring UI) are very important but Panels wants to remain independent from the UI. This makes sense, as each module focus on its duty (Panels on doing its magic, Page Manager in configuring Panels through the UI).

To be more accurated Panels in Drupal 8 can be implemented. Currently, Page Manager and Panelizer implement panels.

So now they are not working together, but eventually they should, that's the target.