I am using Nginx
I have generate a wildcard ssl certificate ie *.example.com
bu using this command
./certbot-auto certonly --server https://acme-v02.api.letsencrypt.org/directory --manual --preferred-challenges dns -d *.example.com
Yes, that's exactly correct. *.example.com will cover subdomains of example.com, but not example.com itself--as a very cursory search would have revealed. If you want to cover example.com on the same cert, you'll need to issue a new cert covering both *.example.com and example.com.