Hello @MarkEWaite our Jenkins environment is specific to a Windows 2022 server, we understand that you have a big footprint over the world, but we are very specific and there was at least one more person reporting this problem that was sent to this thread.
Please check Unable to download and install plugins - #3 by dduportal (The other thread I initially linked): it has a totally different error message. The can’t even reach updates.jenkins.io URL so they don’t get a redirect (yes devil is in the details… of logs 
) while you issue here is with get.jenkins.io’s TLS negociation where “something” in the middle between your server and the remote server does remove some TLS intermediate certificate chain “in some cases” (e.g. when having some specific HTTP request headers).
we did test that my servers can in fact reach out to the repos and are able to manually download plugins, but i will ask again.
I have no doubt you did. But everything points at your network setup:
- Only your network has the issue (I can’t reproduce at all with fresh Windows 2022 VMs)
- There is a Bluecoat appliance in your network which is notoriously known to perform TLS man in the middle => and your issue is with TLS certificate chains.
My educated guess (been in your place years ago) is that your powershell has access to the “Bluecoat TLS certificate chain” in Windows while your JVM does not. Hence you need your bluecoat admin to works with you tu unblock you as their setup is not really RFC standard (and we can’t really help on the Jenkins infra side)