We now have confirmation that BLizzard are aware of and working on a fix for the couch co-op Infernal Hordes issues.
Players have been unable to progress after certain waves, even getting past the final one but seeing the Council room doors not open. This issue seems to be limited to local co-op and has been going on for quite a while. Let’s hope it can be resolves soon, as Infernal Hordes are a key component of this season and the game in general at this point.
Just acknowledging here that the team has been keeping up with the reports and has been investigating/working on this.