SendGrid V3 api with C#. email not sending

is there something wrong with this code? i already put my email in my code but i don't get any email. i have a hint that is it not working because i am using API key ID instead of API key because i can't see my API key because its only show just once. if is that the reason why is this code not working. Is there no way to view your API key again ?

   public string SendEmailMain()
        {
            SendEmail().Wait();

        }
 static async Task SendEmail()
        {
            common com = new common();
            var apiKey = com.sendGridAPI;
            var client = new SendGridClient(apiKey);
            var from = new EmailAddress("[email protected]", "test user");
            var subject = "Sending with SendGrid is Fun";
            var to = new EmailAddress("[email protected]", "teset user");
            var plainTextContent = "and easy to do anywhere, even with C#";
            var htmlContent = "<strong>and easy to do anywhere, even with C#</strong>";

            var msg = MailHelper.CreateSingleEmail(from, to, subject, plainTextContent, htmlContent);
            var response = await client.SendEmailAsync(msg);

        }