Suddenly, the SSL certificate on all of my websites and the ISP control panel stopped working. Now, it gives that scary warning to anyone who visits the site. I thought Let's Encrypt renewed automatically? Can someone help me figure out how to renew it?
What is the error in your browser? Go through this FAQ: https://www.howtoforge.com/community/threads/lets-encrypt-error-faq.74179/
A common mistake is by purging certbot or letsencrypt in order to install a new bleeding edge one. You also supposedly received warning emails from Let's Enxrypt at least twice before expiry for failing to renew that you might had failed to take action. But to be certain, follow the FAQ that @Th0m mentioned above.
