They turned Foundry Play on with the last patch after the season update. You can play missions again.
The Editor is still disabled for maintenance reasons.
There's a pretty major bug since the update which either prevents NPCs from spawning or despawns them if you move too far away. I've tried a number of Foundry missions now only to be unable to complete them due to a missing NPC contact. Beaming out and resuming sometimes works, but not always. This can also happen quite some time into the mission, which is frustrating.
something tells me the devs are probably screaming at the foundry right now seeing as the whole point of taking it down was to prevent stuff like this.