This code result match with Google Authenticator
var base32Bytes = Base32Encoding.ToBytes(key);
var totp = new Totp(base32Bytes);
var totpCode = totp.ComputeTotp();
This code result not match with Google Authenticator
var base32Bytes = Base32Encoding.ToBytes(key);
var totp = new Totp(base32Bytes, totpSize: 6, step: 60);
var totpCode = totp.ComputeTotp();
Google Authenticator URI example
var uriString = new OtpUri(OtpType.Totp, key, "myemail@yahoo.com", "Test Not Working", digits: 6, period: 60).ToString();