I’m a bit confused by your question. According to public records, your site has never had a Let’s Encrypt certificate, and in fact your domain name coastofmain.com doesn’t even exist! Did you mean coastofmaine.com?
Yes, I apologize. The domain is coastofmaine.com. The error in outlook says the certificate has expired as of 3/18/2017. I just don’t know HOW to update it! Here is the error that we see
Did you do something to obtain this certificate, or did your hosting provider obtain it for you? In the latter case, you should ask the hosting provider to renew the certificate for you.