Although this was acknowledged to us via email, posting here as a tracker since now we have a definitive root cause (Zapier doesn’t support Showcase Pages, and at one point did but something changed).
If it helps, from our opinion:
Showcase pages are around a product (generally).
It’s rare that you would use something like Zapier to update a Company page, because it’s really just a placeholder to track who works there, what they do, etc.
Seems like it’s a hierarchy issue that should be a simple fix. If Zapier is trying to post as the Company, that makes no sense, because the Company isn’t a user. Everything is posted as whoever is the admin of the page. Thus, if it’s hardcoded to look at “one level up” when associating the account, seems like the simple fix is to tell it to stop doing that and instead, prompt the user for which “account” should do the post.