Can't get two PS4 controllers working for co-op

[nathan.r.cross]

Hey everyone, I just got the game through Humble and my wife actually was very excited to play the game with me (for once!).

I have two PS4 DS4 controllers connected via USB. I've tried DS4Controller and Steam's own PS4 controller support to enable co-op play in the game. Unfortunately while both controllers are connected and light up, I can only ever get the game to recognize one controller, never two. I can't even seem to set one player to keyboard while the other has a controller.

Just to help clarify what steps I've taken:

1. Tried DS4Controller first -- recognizes two controllers are connected but only one shows up in game. Player 2 controller not recognized/player cannot join
2. Tried running DS4Controller and Steam's native PS4 controller support simultaneously -- neither controller worked.
3. Ran only Steam's native PS4 controller support -- recognizes two controllers are connected and each are registered, but only one shows up in game. Player 2 controller not recognized/player cannot join.
4. At all stages, I tried resetting the controllers with the little hidden button on the back of the controller, as well as unplugging/replugging controllers in and out of game. Also restarted computer and/or Steam after making changes and attempting again.

As an aside, I can't even get two controllers working on Portal 2 co-op. The game only recognizes one controller (no offline co-op play) though both work and both have controller profiles in Steam.

Been at this for a few days now without luck. What am I missing? Has anyone here been able to get two PS4 controllers working with co-op for this game? What was your setup like?

Any help is greatly appreciated!