I would half wonder if its worth testing if this is specific to the hash fragment, or if you’d also have trouble receiving a query parameter at the callback route, but to do so, you would need to switch to using PKCE flow, since implicit flow will always use fragments.
Is the Angular side handling the callback (to get the token), or .NET? From what I understand, hash fragments will not be sent server side (client side only), so you may need to switch to authorization code flow if you are trying to get the tokens directly on the .NET side. Similar conversation found in Auth0’s forum: The redirect response does not send the hash fragment (tokens) to the server-side - #2 by jmangelo - Auth0 Community