Today I wanted to build a new version of the website with Drone. It got this error: "SSL certificate problem: certificate has expired". The strange thing is that SSL certificate is from Let's Encrypt and this is automatically regenerated.
The solution I found was to pull a newer version of "drone/git" on the host machine where Drone runs. This solves the problem.
<a href="https://discourse.drone.io/t/issue-with-letsencrypt-and-ssl-certificates-in-old-drone-git/9852">solution</a>