virtualmin modify-web --all-domains --letsencrypt-renew 2 does NOT work

Hi Forum,
I installed a new server for my websites today. Ubuntu 16.04.2 LTS and Virualmin GPL.
Everythink works so far… then I looked for renew of the SSL Let’s entrypt cert.
I found a way to update new certs.
“virtualmin modify-web --all-domains --letsencrypt-renew 2” - here form the forum.
The output seems to be OK

Updating server wrt***.***-.de …
Saving server details …
… done

Then I checked the Cert SHA-1 fingerprint… it is still the same.
Also the times on the ssl.ca, ssl.cert and ssl.key files did not change.

What have I done wrong?