Trouble getting self hosting web api working over SSL

I have been having some trouble getting SSL enabled for my self hosting web api.

I have been trying with the code below, but if there is a better way of doing this, i would like to know :)

I use this code to generate the cert and register it against a port:

public static X509Certificate2 GenerateCert(string certName, TimeSpan expiresIn)
    {
        var store = new X509Store(StoreName.Root, StoreLocation.LocalMachine);
        store.Open(OpenFlags.ReadWrite);
        var existingCert = store.Certificates.Find(X509FindType.FindBySubjectName, certName, false);
        if (existingCert.Count > 0)
        {
            store.Close();
            return existingCert[0];
        }
        else
        {
            var cert = CreateSelfSignedCertificate(certName, expiresIn);
            store.Add(cert);

            store.Close();
            return cert;
        }
    }

    public static void RegisterSslOnPort(int port, string certThumbprint)
    {
        var appId = Guid.NewGuid();
        string arguments = $"http add sslcert ipport=0.0.0.0:{port} certhash={certThumbprint} appid={{{appId}}}";
        ProcessStartInfo procStartInfo = new ProcessStartInfo("netsh", arguments);

        procStartInfo.RedirectStandardOutput = true;
        procStartInfo.UseShellExecute = false;
        procStartInfo.CreateNoWindow = true;

        var process = Process.Start(procStartInfo);
        while (!process.StandardOutput.EndOfStream)
        {
            string line = process.StandardOutput.ReadLine();
            Console.WriteLine(line);
        }

        process.WaitForExit();
    }

    public static X509Certificate2 CreateSelfSignedCertificate(string subjectName, TimeSpan expiresIn)
    {
        // create DN for subject and issuer
        var dn = new CX500DistinguishedName();
        dn.Encode("CN=" + subjectName, X500NameFlags.XCN_CERT_NAME_STR_NONE);

        // create a new private key for the certificate
        CX509PrivateKey privateKey = new CX509PrivateKey();
        privateKey.ProviderName = "Microsoft Base Cryptographic Provider v1.0";
        privateKey.MachineContext = true;
        privateKey.Length = 2048;
        privateKey.KeySpec = X509KeySpec.XCN_AT_SIGNATURE; // use is not limited
        privateKey.ExportPolicy = X509PrivateKeyExportFlags.XCN_NCRYPT_ALLOW_PLAINTEXT_EXPORT_FLAG;
        privateKey.Create();

        // Use the stronger SHA512 hashing algorithm
        var hashobj = new CObjectId();
        hashobj.InitializeFromAlgorithmName(ObjectIdGroupId.XCN_CRYPT_HASH_ALG_OID_GROUP_ID,
            ObjectIdPublicKeyFlags.XCN_CRYPT_OID_INFO_PUBKEY_ANY,
            AlgorithmFlags.AlgorithmFlagsNone, "SHA512");

        // add extended key usage if you want - look at MSDN for a list of possible OIDs
        var oid = new CObjectId();
        oid.InitializeFromValue("1.3.6.1.5.5.7.3.1"); // SSL server
        var oidlist = new CObjectIds();
        oidlist.Add(oid);
        var eku = new CX509ExtensionEnhancedKeyUsage();
        eku.InitializeEncode(oidlist);

        // Create the self signing request
        var cert = new CX509CertificateRequestCertificate();
        cert.InitializeFromPrivateKey(X509CertificateEnrollmentContext.ContextMachine, privateKey, "");
        cert.Subject = dn;
        cert.Issuer = dn; // the issuer and the subject are the same
        cert.NotBefore = DateTime.Now;
        // this cert expires immediately. Change to whatever makes sense for you
        cert.NotAfter = DateTime.Now.Add(expiresIn);
        cert.X509Extensions.Add((CX509Extension)eku); // add the EKU
        cert.HashAlgorithm = hashobj; // Specify the hashing algorithm
        cert.Encode(); // encode the certificate

        // Do the final enrollment process
        var enroll = new CX509Enrollment();
        enroll.InitializeFromRequest(cert); // load the certificate
        enroll.CertificateFriendlyName = subjectName; // Optional: add a friendly name
        string csr = enroll.CreateRequest(); // Output the request in base64
        // and install it back as the response
        enroll.InstallResponse(InstallResponseRestrictionFlags.AllowUntrustedCertificate,
            csr, EncodingType.XCN_CRYPT_STRING_BASE64, ""); // no password
        // output a base64 encoded PKCS#12 so we can import it back to the .Net security classes
        var base64encoded = enroll.CreatePFX("", // no password, this is for internal consumption
            PFXExportOptions.PFXExportChainWithRoot);

        // instantiate the target class with the PKCS#12 data (and the empty password)
        return new System.Security.Cryptography.X509Certificates.X509Certificate2(
            System.Convert.FromBase64String(base64encoded), "",
            // mark the private key as exportable (this is usually what you want to do)
            System.Security.Cryptography.X509Certificates.X509KeyStorageFlags.Exportable
        );
    }

I call this code from:

private static void SetUpWebApi()
    {
        
        try
        {
            Trace.WriteLine("Setting up web service on " + appsettings.ApiUrl);

            int port = 50244;
            var certSubjectName = "*.dogoffice.co.uk";
            var expiresIn = TimeSpan.FromDays(7);
            var cert = Cert.RegisterCertificate.GenerateCert(certSubjectName, expiresIn);

            Console.WriteLine("Generated certificate, {0}Thumbprint: {1}{0}", Environment.NewLine, cert.Thumbprint);

            Cert.RegisterCertificate.RegisterSslOnPort(50243, cert.Thumbprint);


            string url = "https://+:" + port;
            WebApp.Start<StartUp>(url);
      
            Trace.WriteLine($"Web service started at: {DateTime.UtcNow:D}  at Url: {url}");
            
        }
        catch (Exception ex)
        {
            Trace.WriteLine(ex.Message);
        }

    }

I then have a test app, which calls the code like so:

        public static bool ConnectTest(string username, string password)
    {
        using (HttpClient client = new HttpClient())
        {
            var auth = Convert.ToBase64String(
                System.Text.Encoding.ASCII.GetBytes(
                    string.Format("{0}:{1}", username, password)));

            client.DefaultRequestHeaders.Authorization =
                new AuthenticationHeaderValue(
                    "Basic",
                   auth);


            HttpResponseMessage httpr = client.GetAsync("https://127.0.0.1:50244/" + "/api/system/connecttest").Result;
            var result = httpr.Content.ReadAsStringAsync();

            bool connected = false;
            bool.TryParse(result.Result, out connected);


            return connected;
        }
    }

When I run the code I get the following error:

AuthenticationException: The remote certificate is invalid according to the validation procedure.

When I browse to the URL https://127.0.0.1:50244/api/system/connecttest. I hit the end point, however it says the certificate is not secure and the certificate is OK.

Any ideas to how to get this working?

Regards,

Ben