When i submit the registration form i get this error:

System.ArgumentNullException: 'String reference not set to an instance of a String. Parameter name: s'

it's coming form the hashing password class

public static class Crypto
{
    public static string Hash(string value)
    {
        return Convert.ToBase64String(
            SHA256.Create()
                .ComputeHash(Encoding.UTF8.GetBytes(value)));
    }
}