I'm assuming that the missing s in sudo and the inclusion of -d https://promo.edupeer.com were oversights. Let's Encrypt currently does not certify URLs. I'm not sure why you would need to certify www.promo.edupeer.com, but that's up to you.
If JuergenAuer's theory is correct (and I believe it is), you can use the following certbot command to have certbot automatically restart your webserver when your certificate is updated: