Getting Scope Validating error in Identity Server 4 using JavaScript Client in asp.net core

While your client (application) is configured or allowed to request the openid resource (or scope), your identity server is not configured for the openid identity resource

You need to add it as an identity resource similar to how its done here and have a method that returns all your identity resources that you want to use like its done here.

In short add a new method to your Config.cs that looks like this:

public static List<IdentityResource> GetIdentityResources()
{
    return new List<IdentityResource>
    {
        new IdentityResources.OpenId(),
        new IdentityResources.Profile() // <-- usefull
    };
}

And then to your identityservers service container add your identity resource configuration like this:

 services.AddIdentityServer()
    .AddTemporarySigningCredential()
    .AddInMemoryApiResources(Config.GetApiResources())
    .AddInMemoryClients(Config.GetClients())
    .AddInMemoryIdentityResources(Config.GetIdentityResources()); // <-- adding identity resources/scopes