Hunter B Thanks for your patience and sharing it with us.
Update for the community:
Initially when following the tutorial, App registrations were not created under Azure AD B2C. Then after assigning necessary permissions and troubleshooting, Hunter B figured out that Azure Function name was created incorrectly i.e.,
hello in the tutorial. Hence, the API call was made incorrectly and returned the above error.
He corrected the function name and it worked successfully.