Configure AD Groups to use with Roles in .NET Core (C# 8) MVC

I am trying to use policy based authorisation in an MVC app in C# .NET CORE (8) , using membership of OnPrem AD groups to assign roles .

This is a snippet of the appsettings.json telling the system I want to grant the Admin role to members of AD Group1, and so on for the Editors & Readers roles :

"AppConfig": {

  "Admins": "AD Group1",

  "Editors": "AD Group2",

  "Readers": "AD Group3",

  "DBConnstr2": "myconnstr"

}

This is a snippet of the Program.cs to actually apply the policy

var Admins = builder.Configuration["AppConfig:Admins"];

var Editors = builder.Configuration["AppConfig:Editors"];

var Readers = builder.Configuration["AppConfig:Readers"];

builder.Services.AddAuthorization(options =>

{

    options.AddPolicy("Admins", policy => policy.RequireRole(Admins));

    options.AddPolicy("Editors", policy => policy.RequireRole(Editors));

    options.AddPolicy("Readers", policy => policy.RequireRole(Readers));

});

These roles are used in the MVC controllers to apply permissions to each function

        [Authorize(Policy = "Readers")]

        public async Task<IActionResult> Index(){

}

The problem is that some of the AD Groups do not get mapped into roles, for example my user claims lists me as a member of AD Group1 , 2 & 3, but the roles I have do not include the Editors role ( I get the role when I set a different group in AppConfig:Editors). This suggests that something is different about how Group2 is set up.

What is causing this, & what do I need to do get AD Group 2 behaving in the same way as Groups 1 & 3?

Thanks in advance