Core 5.0 project references Framework 4.7.2 project and throws'System.Security.Cryptography.SHA256Cng' error

The framework project is running a method that gets an access token for AAD to dynamics 365 crm and returns it as a request header. The error from running the GetAuthHeader is

One or more errors occurred. (Could not load type 'System.Security.Cryptography.SHA256Cng' from assembly 'System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.)

I've tried researching it and I'm wondering if I'm using the wrong framework version? Any help is greatly appreciated. Both methods shown below are using Framework 4.7.2.

I'm using the PowerApps-Samples, specifcally the CDSWebApiService at https://github.com/microsoft/PowerApps-Samples/tree/master/cds/webapi/C%23/CDSWebApiService

Method below throws error when called:

private AuthenticationHeaderValue GetAuthHeader()
        {
            AuthenticationResult authResult;
            if (_credential == null)
            {
                authResult = _authContext.AcquireTokenAsync(
                    serviceUri, clientId, 
                    new Uri(redirectUrl), 
                    new PlatformParameters(PromptBehavior.Auto)).Result;
            }
            else
            {
                authResult = _authContext.AcquireTokenAsync(serviceUri, clientId, _credential).Result;
            }
            return new AuthenticationHeaderValue("Bearer", authResult.AccessToken);
        }

The method calling this is shown below. The call to the above GetAuthHeader is what throws the exception:

protected override Task<HttpResponseMessage> SendAsync(
                  HttpRequestMessage request, CancellationToken cancellationToken)
        {
            try
            {
                request.Headers.Authorization = GetAuthHeader(); //This throws the error
            }
            catch (Exception ex)
            {

                throw ex;
            }
            return base.SendAsync(request, cancellationToken);
        }

In short, it's not supported in .NET Core, You probably should update your .NET version/runtime.