If you’re using Debian 7 a.k.a wheezy which is end of life at this moment and you were using Let’s Encrypt was your SSL, then you might need some backward compatibility to continue. A possible work around for me as below:

wget https://raw.githubusercontent.com/certbot/certbot/75499277be6699fd5a9b884837546391950a3ec9/certbot-auto
chmod +x ./certbot-auto
./certbot-auto --no-self-upgrade

For renewing an existing certificate you can use the following command instead:

./certbot-auto --no-self-upgrade