I have a lot of sites being powered by EE and all of them are using Lets Encrypt for SSL. Each installation is on it's own VPS with it's own dedicated IP Address. Every one of the websites was able to utilize the Lets Encrypt SSL Certificate and is able to renew the certificate if I issue the command manually, but not one of the instances has ever auto-renewed an SSL Certificate, via crontab.
When I'm logged into the console/terminal with my user account and issue the "crontab -l" command, I get:
0 0 * * 0 ee site update --le=renew --all 2> /dev/null # Renew all letsencrypt SSL cert. Set by EasyEngine
This reads the exact same when I run the "crontab -l" command as the root user.
There is only one site per VPS and it looks like it is set up to work correctly.
Also, I NEVER get a system generated email about SSL Certificate Success nor Failures.