Common fixes

Invalid certificates

Symptoms

• the site gives a "ERR_CERT_DATE_INVALID" error when loading https://hedonometer.org.
• some pages work partially from the http site (and the Chrome Dev Tools show the above error for specific files).

Fixes

1. ssh onto server, get root (sudo su).
2. Find the command to renew certs, history | grep certbot.
3. Run ./certbot-auto renew.