It is always better to use Thumbprint of the certificate to get the certificate. Please make sure you have created the certificate correctly. Also please check you have placed the certificate in Personal certificate section in Local Machine. You can check this using MMC snap in. please try below code..
var store = new X509Store(StoreName.My, StoreLocation.LocalMachine);
store.Open(OpenFlags.OpenExistingOnly | OpenFlags.ReadOnly);
var certificate = store.Certificates
.Cast<X509Certificate2>()
.SingleOrDefault(c => string.Equals(c.Thumbprint, “CertificateThumbprint”, StringComparison.OrdinalIgnoreCase)); // please replace CertificateThumbprint with original Thumbprint