The only thing I can think of is that you picked “new extension” from Create New Project:
And for whatever reason the rig is using a blank/default extension or hasn’t pulled the secret down over the API.
You may need to refresh manifest
And/or when creating a view set it to a “real” user rather than the “Developer Rig” user. (Ticking Use Current user works correctly for me)
But I’m not sure as ever extension I have loaded uses the Real ExtensionClientID/Secret, but then they are all pointed at real ID’s for the Frame Properties
Also make sure your Rig is up to date (current version is v1.2.1)
Or consider remaking the project in the rig.
Additionally the problem may stem from having selected a template to create a project from rather than starting fresh.