Error AADSTS50049 when testing 0-call-api-vanillajs

> Please provide us with the following information:
> ---------------------------------------------------------------

### This issue is for a: (mark with an `x`)
```
- [x] bug report -> please search issues before submitting
- [ ] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Minimal steps to reproduce
> Followed instructions in README.md for the sample in a trial Entra tenant. App registrations created and config files updated.
> Both dotnet (API) and node (SPA) samples running
> Visited localhost:3000 and clicked the 'Sign-in' link. Small pop-up (size of normal 'login or register' or 'pick account' style screen) flashed momentarily then closed before loading any content.

### Any log messages given by the failure
> AADSTS50049: Unknown or invalid instance

{
"error": "invalid_instance",
"error_description": "AADSTS50049: Unknown or invalid instance. Trace ID: 4bb4a35a-fe66-4c56-b09b-754782482900 Correlation ID: 57cc2ed3-5425-47ae-bec5-46115860868b Timestamp: 2023-11-27 15:26:54Z",
"error_codes": [
50049
],
"timestamp": "2023-11-27 15:26:54Z",
"trace_id": "4bb4a35a-fe66-4c56-b09b-754782482900",
"correlation_id": "57cc2ed3-5425-47ae-bec5-46115860868b",
"error_uri": "https://login.microsoftonline.com/error?code=50049"
}

### Expected/desired behavior
> Login/register popup expected to load

### OS and Version?
> Windows 11 23H2 22631.2787; Node v21.2.0

### Versions
>

### Mention any other details that might be useful

> ---------------------------------------------------------------
> Thanks! We'll be in touch soon.

Beginne mit README.md und den aktualisierten Konfigurationsdateien für das Beispiel 0-call-api-vanillajs, starte dann die Node SPA unter localhost:3000 und untersuche den Authentifizierungsablauf des Sign-in-Links. Vergleiche die Tenant- und Instance-Einstellungen mit dem gemeldeten AADSTS50049-Fehler; als erledigt gilt die Aufgabe, wenn das Login/Register-Popup geladen wird, statt sich sofort zu schließen.

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