Unable to find plugins in list of available plugins in jenkins

Go to: Manage Jenkins → Manage Plugins → Advanced, then click Check now in the bottom right-hand corner. When you go back to Available tab all plugins should be listed.

For me the following worked:

Go to Manage Jenkins->Configure Global Security

Click the checkbox for "Use browser for metadata download"

I also have security disabled and prevent cross site forgery unchecked.

At the plugins section of Jenkins open the "Advanced Settings" tab and paste the following URL into the Update Server URL field (at the bottom): https://updates.jenkins.io/update-center.json