.net5 secrets.json not being used locally

Question

I have a .net5 web app in which I am trying to add a secrets.json file so I have right clicked and created the file - in my project file I can see:

<PropertyGroup>
  <TargetFramework>net5.0</TargetFramework>
  <UserSecretsId>1cb5a573-309c-4b03-b7e9-3c09794038bb</UserSecretsId>
</PropertyGroup>

The secrets.json file exists in AppData\Roaming\Microsoft\UserSecrets\1cb5a573-309c-4b03-b7e9-3c09794038bb:

{
  "GraphApi": {
    "ClientSecret": "secret-key"
  },
}

In my appsettings.json:

"GraphApi": {
  "TenantId": "tenant-id",
  "Scopes": ".default",
  "ClientId": "client-id",
  "ClientSecret": "From user secrets"
},

and in my program.cs:

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            })
            .ConfigureAppConfiguration((hostContext, builder) =>
            {
                if (hostContext.HostingEnvironment.IsDevelopment())
                {
                    // Use user secrets for local development
                    builder.AddUserSecrets<Program>();
                }
            });

however, it's not picking up my ClientSecret from the secrets.json - if I put the value in appsettings.json, it works just fine - is there anything else I need to do to make it work?