My initial suspicion is that this is a local configuration issue. Unfortunately, you've not provided any information related to your local configuration, so there is no way that others can guide you or help you as you seek a solution for the issue.
Please refer to "How to report an issue" for the types of information that others will need if they are going to help you.
In this specific case, others will probably want to know things like:
- What JDK version are you using? (java -version)
- What operating system are you using?
- What version of plugin installation manager tool are you using?
- Have any local modifications been done to the Java SSL certificate management?
- Are you accessing the internet through a proxy?
- Which mirror is reported as the first choice when you open https://updates.jenkins.io/latest/git.hpi?mirrorlist in your web browser?
- Can you download a plugin from your web browser with https://updates.jenkins.io/latest/git.hpi ?