prisma-auth0-example: Authorization error

After adding http://localhost:8000 to “Allowed Web Origins” in the Auth0 client console I was able to test login, but then I get:

auth.js:51:
{error: "access_denied", errorDescription: "Invalid URI "undefined/users/YXV0aDB8NWE4OWI1OTMzYWZmNzMxMDEzMjUxNzY5.json?auth=undefined"", state: "5p8LD.2Jl27.2uD1ot6wdwAqCNX0j5Bq"}