I know I'm not very active here in the community but I did a little step by step that should help especially those who use DNS CloudFlare.
Edit the LetsEncrypt configuration file:
nano /etc/letsencrypt/config/account.conf
Insert the line:
DEFAULT_CA=https://acme-v02.api.letsencrypt.org/directory
Enter your cloudFlare token and email with the parameters below:
SAVED_CF_Key='token'
SAVED_CF_Email='cloudflare-email'
Then save the file and restart the services with:
wo stack restart
Now you should be able to issue SSL with:
wo site update dominio.com --le --dns=dns_cf
I also made a short step-by-step video.
Hope Google Translate translated well.