Calling WebAPI with authorisation from server side blazor - authorization

Question

Apologies if this is a bit of a dumb question - I'm trying to get my head round security setup and don't have much experience in this area. Been reading as much as I can, but can't find a clear example for what I'm trying to do.
I have created the default server-side and wasm blazor projects from the visual studio templates, and have shared the wasm project so I can re-use both client-side and server-side as per Carl Franklin's article:
http://www.appvnext.com/blog/2020/2/2/reuse-blazor-wasm-ui-in-blazor-server
That all works fine.
Next, I repeat, but add the "Individual User Accounts" option to both projects when creating, set the db string to a shared identity database. Both work individually, however, when I share the client code, and call from server-side blazor, the webapi call fails with an "unauthorized" error.
So, in short, I'm logging into the server-side blazor project successfully. The failure happens when I attempt to call the webapi which now sits in a separate project (the WASM project) and so will run in a different domain (don't think I'm hitting cors problems yet). When I attempt to call the webapi I get the unauthorized error. When I run in WASM, it all works as expected.
Can someone please give me a pointer on what steps I need to take to get this working? Full code for the razor component is below...
#page "/fetchdata"
#using Microsoft.AspNetCore.Authorization
#using Microsoft.AspNetCore.Components.WebAssembly.Authentication
#using BlazorWasm.Shared
#attribute [Authorize]
#inject HttpClient Http
<h1>Weather forecast</h1>
<p>This component demonstrates fetching data from the server.</p>
#if (forecasts == null)
{
<p><em>Loading...</em></p>
}
else
{
<table class="table">
<thead>
<tr>
<th>Date</th>
<th>Temp. (C)</th>
<th>Temp. (F)</th>
<th>Summary</th>
</tr>
</thead>
<tbody>
#foreach (var forecast in forecasts)
{
<tr>
<td>#forecast.Date.ToShortDateString()</td>
<td>#forecast.TemperatureC</td>
<td>#forecast.TemperatureF</td>
<td>#forecast.Summary</td>
</tr>
}
</tbody>
</table>
}
#code {
private WeatherForecast[] forecasts;
protected override async Task OnInitializedAsync()
{
try
{
string url = "https://localhost:44378/WeatherForecast";
forecasts = await Http.GetFromJsonAsync<WeatherForecast[]>(url);
}
catch (AccessTokenNotAvailableException exception)
{
exception.Redirect();
}
catch(HttpRequestException exception)
{
string msg = exception.Message;
}
}
}