In this thread, Zero gave us this update:

We are re-enabling PLAYING of Foundry missions now.

The editor will remain disabled. During this time, reviewing of Foundry missions will also be disabled.

I’ll be creating a thread in the Foundry bug forums for authors (and other players) to post any bugs they see that weren’t present before Season 6.

Thank you all for your assistance and your patience.

EDIT:
The republishing of all the missions is still in progress, so Don’t Panic if you don’t see one of yours there.

while rehpic added:

Note that the republish we started last night is only done with about 60% of previously published projects. If your project is missing do not panic, it is most likely just not been republished yet. We estimate that the republish should be done with all projects in about 10 to 12 hours.