I am installing the ec2-plugin (https://github.com/jenkinsci/ec2-plugin) using the install-plugins.sh (in a Dockerfile).

The plugins.txt file that I supply to the install script has the plugin listed as "ec2:1.4.3".

The plugin is located at http://mirrors.jenkins-ci.org/plugins/ec2/1.43/ec2.hpi (as expected by the plugins.txt).

When the install-plugins.sh script looks for it, it attempts to download from a different location. Here are the relevant log messages from the Jenkins installation:

Downloading plugin: ec2 from https://updates.jenkins.io/download/plugins/ec2/1.4.3/ec2.hpi

...

03:13:20 Failed in the last attempt (curl -sSfL --connect-timeout 20 --retry 3 --retry-delay 0 --retry-max-time 60 https://updates.jenkins.io/download/plugins/ec2/1.4.3/ec2.hpi -o /usr/share/jenkins/ref/plugins/ec2.jpi)
Downloading plugin: ec2-plugin from https://updates.jenkins.io/download/plugins/ec2-plugin/1.4.3/ec2-plugin.hpi

...

03:13:35 Failed in the last attempt (curl -sSfL --connect-timeout 20 --retry 3 --retry-delay 0 --retry-max-time 60 https://updates.jenkins.io/download/plugins/ec2-plugin/1.4.3/ec2-plugin.hpi -o /usr/share/jenkins/ref/plugins/ec2-plugin.jpi)
Failed to download plugin: ec2 or ec2-plugin

...

Some plugins failed to download! Not downloaded: ec2