I had the same issue, struggled for a while, then I noticed that as long as I was in "Unformatted citation mode" the bibliography wouldn't display. If you are in "Unformatted citation mode", the references display in blue. Otherwise, they display as normal text (but still have the link, ofc).
From google doc, Addons -> Paperpile -> Manage citations / Then the setting icon -> Unformat citations
When you revert to NOT unformatted citations, the biblio displays after updating. But it's not clear to me how I managed to revert yet