Debian 9 / Ubuntu 18.04 LetsEncrypt Error

Hi @Raphael, i tried to rebuild my VPS again as Debian 9 using

bash hst-install.sh -v no -k no -s mydomain -e my@email -p password

After reboot,mydomain is not added to the Mail section of hcpanel. I have to manually add it. (Is this the case? I think previous installers automatically register the mydomain as mailserver.)

I ran v-add-letsencrypt-host but only the Web section mydomain is SSLed. Mail section mydomain is still not SSLed.

I also tried to edit mydomain in the Mail section, and manually click Enable/Use LE. Prompt is: Error: Let’s Encrypt validation status 400

Tried using Cloudflare SSL Off, SSL Full, SSL Flexible, Low, Off, Under development, DNS only modes. Still no luck.