Shared Accounts for a Pack in Published Docs

I’m trying to do a Cross-Doc Action in a published doc

In my published doc I would like to allow people to use a cross doc action into a separate doc.

I’m trying to add a “submit your doc” feature to the play doc, but I don’t want the source doc to be permanently editable. That means that I’ll have to store their submissions in a separate doc.

I thought I could achieve this with a Cross Doc Action. It used to work, but now it seems I cannot hit submit, even if I’m logged in.

This is strange because I set up the credentials as a shared account:

Meanwhile, if I’m logged in with my main account on the published page in play mode it does work.

So it would seem that what needs to be supported is shared accounts for a Pack in published docs.