To access the Grouper Demo, you need an IdP that sends an EPPN.
ProtectNetwork will not do that for the Grouper Demo site.
If your IDP does not sends an EPPN, you may want to use the social options (Google, Facebook, Twitter).
You register first. Then you go back to the Demo jump page and click on the UI. The Grouper Team will get an email when you register, and will add you to a folder with STEM privileges so you can create objects.