Can't get certbot to install!

I'm trying to install certbot on the instance where we have a Bitnami Trac/SVN stack and a Tomcat server installed, and when I do

yum install -y certbot python2-certbot-apache
I keep getting
No package certbot available.
No package python2-certbot-apache available.
Error: Nothing to do

But it worked fine on another (newer) instance, the one hosting our web site!

/etc/os-release on the Trac/SVN/Tomcat instance (the one where it won't install) shows:

NAME="Amazon Linux AMI"
VERSION="2018.03"
ID="amzn"
ID_LIKE="rhel fedora"
VERSION_ID="2018.03"
PRETTY_NAME="Amazon Linux AMI 2018.03"
ANSI_COLOR="0;33"
CPE_NAME="cpe:/o:amazon:linux:2018.03:ga"
HOME_URL="http://aws.amazon.com/amazon-linux-ami/"

while on the web site instance (the one where it was successfully installed), it shows:

NAME="Amazon Linux"
VERSION="2"
ID="amzn"
ID_LIKE="centos rhel fedora"
VERSION_ID="2"
PRETTY_NAME="Amazon Linux 2"
ANSI_COLOR="0;33"
CPE_NAME="cpe:2.3:o:amazon:amazon_linux:2"
HOME_URL="https://amazonlinux.com/"

Can anybody explain what's going wrong? And what can be done about it?

I've tried what was suggested at https://stackoverflow.com/questions/53545436/no-package-certbot-available , with no success.