Folio Builder Panel for InDesign 31.0.1
Publish with an existing custom viewer that cannot be updated
Otherwise you should install the most recent version of the Folio Producer tools. The panel update is available as a separate download to ensure that the panel stays in sync with the DPS Services on the web.
Updating only the panel gives you the flexibility to keep using an older version of the tools to publish folios for previously created viewer apps.