All certificates are expired or expiring - nothing renewing

[mrmarkuz (Markus Neuberger)]

You could use your browser or curl to check certs and dates:

SSL certificate error ERR_CERT_DATE_INVALID

It can be an expired certificate? You can inspect the certificate expiration dates with your browser, or a command like curl -v https://mattermost.example.org 2>&1 >/dev/null | grep '^\* ' As I just wrote the update for another Bug, I ask you: do you have Webtop installed on the same node? See Latest issue with LetsEncrypt.