We're rolling out a patch today on all platforms. This has a few fixes, listed below, but the critical change is an upgrade to the multiplayer backend system. This upgrade has no effect on multiplayer gameplay or functionality, but it's not backward-compatible so everyone needs to get it.
While these patches are rolling out to each platform, you'll see fewer rooms than usual in your multiplayer lobby, as some players will have the update while others don't.
Fixes and changes:
* Multiplayer now requires IPv6 (required by Apple now, which forced us to upgrade it on all platforms)
* Adjustment to Limpy's howl audio timing